89 Fifth Avenue, 7th Floor New York, NY White Paper. HP Thin Technologies A Competitive Comparison

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1 89 Fifth Avenue, 7th Floor New York, NY White Paper HP Thin Technologies A Competitive Comparison

2 Printed in the United States of America Copyright 2012 Edison Group, Inc. New York. Edison Group offers no warranty either expressed or implied on the information contained herein and shall be held harmless for errors resulting from its use. All products are trademarks of their respective owners. First Publication: September 2012 Produced by: Chris M Evans, Sr. Analyst; John Nicholson, Sr. Analyst; Barry Cohen, Editor-in- Chief; Manny Frishberg, Editor

3 Table of Contents Executive Summary 1 Introduction 2 Objective 2 Audience 2 Terminology 2 Overview 3 Thin Provisioning Overview 3 Thin Provisioning Drawbacks 4 HP 3PAR StoreServ Thin Technology 5 Competitive Analysis 6 EMC VMAX 6 Background 6 HP 3PAR StoreServ Comparison Start Thin 6 HP 3PAR StoreServ Comparison Get Thin 7 HP 3PAR StoreServ Comparison Stay Thin 7 VMAX Restrictions 7 NetApp 8 Background 8 HP 3PAR StoreServ Comparison Start Thin 8 HP 3PAR StoreServ Comparison Get Thin 9 HP 3PAR StoreServ Comparison Stay Thin 9 Hitachi VSP 9 Background 9 HP 3PAR StoreServ Comparison Start Thin 10 HP 3PAR StoreServ Comparison Stay Thin 10 EMC VNX 11 HP 3PAR StoreServ Comparison Start Thin 11 HP 3PAR StoreServ Comparison Get Thin 11 HP 3PAR StoreServ Comparison Stay Thin 11 Performance Considerations 12 IBM XIV 12 HP 3PAR StoreServ Comparison Start Thin 12 HP 3PAR StoreServ Comparison Get Thin 12 HP 3PAR StoreServ Comparison Stay Thin 13 Testing Overview and Methodology 14 Test 1 Zero-Page-Reclaim Performance 14

4 Test 2 Large Pre-Allocation 15 Test Results 16 Test 1 Zero-Page-Reclaim Performance 16 Test 2 Large Pre-Allocation 19 Conclusions and Recommendations 21 Best Practices 21 Appendix A Document References 23 Appendix B Test Equipment Specification 24 Arrays 24 Servers 24

5 Executive Summary As the drive to "do more with less" becomes a mantra for many organizations, optimizing space utilization is a key goal of many IT departments. Storage continues to be one of the major cost components of today's infrastructure deployments. Thin technology, including thin provisioning, offers efficiency benefits that can significantly reduce both capital and operational costs. However implementations of thin technologies differ with the storage vendors. HP 3PAR StoreServ is seen as a leader in thin technology, with three key aims: 1. Start Thin ensure thin provisioned storage occurs with minimum overhead. 2. Get Thin ensure data moved to HP 3PAR StoreServ remains thin on migration. 3. Stay Thin ensure data is kept at optimal efficiency over time. To validate this statement, a literature review, extensive customer interviews, and two tests were performed: 1. Zero-Page-Reclaim Performance validation of the ability to reclaim freed resources as part of normal operations. 2. Large Pre-allocation test of the ability to create new storage volumes with minimal overhead. Overall, HP 3PAR StoreServ was the best performer in achieving the goals of "start thin," "get thin," and "stay thin." Edison: HP Thin Technologies Comparison Page 1

6 Introduction Objective This report looks at thin provisioning technology from the major storage vendors in today's marketplace. It compares the thin implementations from seven storage array platforms, including Hewlett Packard's 3PAR storage arrays. In particular this white paper highlights three important differentiating aspects of HP 3PAR StoreServ's thin technology: 1. The ability to "start thin" provisioned storage is thin at deployment time. 2. Getting thin the ability to move data from thick to thin. 3. Staying thin maintaining thin LUNs. Audience Decision makers in organizations that are considering implementing a thin technology strategy will find this paper provides high level information on vendor offerings. Technical professionals looking to understand more about the implementation of vendor thin technology solutions will also find the content of this paper useful. Terminology This white paper makes reference to the following common terminology: "Thick" LUN a storage volume presented from an array in which all of the space representing the logical size of the LUN (logical unit number) is reserved on the array for exclusive use by that volume. "Thin" LUN a storage volume presented from an array that is not tied to any physical storage allocation and in which only the physically written space is consumed on the array. Thin technologies a suite of features, including thin provisioning, that optimize the use of a storage array. Edison: HP Thin Technologies Comparison Page 2

7 Overview In recent years storage has become one of the major cost components within the data center. Although the price of storage continues to fall, the rate of data growth in many organizations continues to rise steeply, resulting in increasing costs for managing the storage systems. Every year there is a requirement to "do more with less," using storage more efficiently without increasing the operational budget. There are a number of key initiatives being undertaken by organizations in order to reduce their storage consumption. These relate directly to the use of thin technology. Reducing Waste Storage utilization never reaches 100 percent of the physical space provisioned from an array, as each level of configuration from the array to the host introduces some inefficiency. Reducing waste increases utilization and allows the deferral of additional capital expenditure. Reducing Overhead Deploying storage isn t a quick task; from purchase order to deployment on the data center floor, the process can take months to achieve. Storage administrators usually keep storage in reserve in order to manage the purchase process. Flexibility End users want the minimum disruption to their applications and as a result, many over-order storage resources, in many cases up to 36 months ahead of when the space is actually needed. Ideally, end users should be able to lay out their storage needs based on growth plans and then allocate that storage on-demand. Improving Cost Efficiency Storage Tiering (placing data on the most cost-effective media for the I/O profile required) is a key technology in reducing storage costs. Dynamic tiering can be used to automate the process of data placement, based on the use of storage pools for LUN creation. Thin provisioned LUNs directly aid the deployment of a tiered storage model. A thin LUN is built from blocks of physical disk capacity from within a pool of storage with metadata to associate the logical LUN to the physical space. The physical blocks can therefore be taken from multiple pools, where each pool represents a different tier. Thin Provisioning Overview Thin provisioning is a space reduction technology implemented by all of the major enterprise storage vendors. It enables the utilization of storage within an array to be increased over traditional "thick" storage deployments. Edison: HP Thin Technologies Comparison Page 3

8 In traditional "thick" storage deployments, physical space on disk is immediately reserved for the entire size of a volume (or "LUN") at creation time, regardless of how much space will subsequently be used by the host. In thin storage deployments, no space is reserved in advance for the LUN. As the host writes data to the LUN, physical space is assigned on-demand from the array, usually in blocks that vary from 4KB to 42MB, according to the vendor. Thin provisioned LUNs are therefore much more efficient and more closely track the actual space in use on the host. For many reasons, storage utilization on hosts never reaches 100 percent utilization. However with "thick" LUNs, physical space is reserved out on an array for the entire size of a volume. Thin provisioned deployments can take advantage of all physical storage available by creating more logical storage capacity than is physically available. So called "over-provisioning" enables the utilization of physical space to be pushed to levels higher than can be achieved in normal deployments. Thin Provisioning Drawbacks The ability to over-provision storage does come with a few drawbacks. Should physical space be completely exhausted, hosts will receive write errors, indicating a physical problem on the array. Write failures are not usually handled gracefully by the host operating system and can lead to system crashes. Therefore, physical versus logical space capacity needs to be carefully managed. Over time as files are created and deleted, thin LUNs become less efficient. This is due to the way in which the file system on the LUN manages file allocations, free space and metadata. Some file system implementations are more "thin friendly" than others and are designed to re-use released space. However, housekeeping of thin provisioned storage is required in order to maintain optimal levels of efficiency. Storage vendors have introduced features that enable the array to recover unused storage resources: Zero-Page-Reclaim (ZPR) A storage array identifies an entire block of storage consisting of binary zeros, the block will be assumed to be unused and is released back to the free pool. The ability to find unused blocks depends on a number of factors, including the file system and array block-size and the level of file fragmentation. Smaller array block-sizes are better for ZPR operations. SCSI UNMAP The UNMAP command is a low-level I/O operation that can be used by the host to signal to the storage array that a block of storage is no longer in use and can be released to the free pool. Unfortunately very few operating systems currently support this feature. Edison: HP Thin Technologies Comparison Page 4

9 HP 3PAR StoreServ Thin Technology The HP 3PAR StoreServ storage platform has a "thin by design" architecture that places no restrictions on the use of either thin or thick LUNs. This applies to LUN performance, and capacity, removing the need for the storage administrator to design the layout of the array to cater for thin technology. HP 3PAR StoreServ is specifically optimized for thin provisioning and contains many unique design features that enable "starting thin," "getting thin," and "staying thin." RAID MP (multi-parity) HP 3PAR StoreServ arrays implement a form of RAID-6 that divides physical disks into "chunklets" of either 256MB or 1GB in size. Chunklets are combined to form Logical Volumes (LVs) and Common Provisioning Groups (CPGs) from which Virtual Volumes are created. Thin Provisioning Virtual Volumes use a block size increment of 16KB, which is the minimum reclaimable unit of storage within the array. Hardware ASIC Now at Generation Four, HP 3PAR StoreServ uses dedicated custom ASIC (Application Specific Integrated Circuit) processors to perform the identification and recovery of unused resources that can be reclaimed from thin provisioned virtual volumes. An ASIC enables processor-intensive tasks to be offloaded to dedicated hardware, removing the performance impact of features such as space reclamation from the array and ensures consistent host I/O response times. The HP 3PAR StoreServ ASIC provides a range of functions, including inline ZPR. Thin Persistence An operating system task that identifies and recovers freed resources. Thin Conversion Performs the migration of thick to thin volumes through a process of inline zero detection. As data is copied to the array, zeroed blocks of data are identified and logically mapped rather than physically written to disk. Thin Copy Reclamation Performs space recovery on volume copies within the array. Thin Reclamation API HP 3PAR StoreServ developed the Thin Reclamation API in partnership with Symantec. This feature allows the file system to signal when freed resources can be released on the array. It is supported by Symantec Veritas Storage Foundation from Version 5 onwards. Virtualization Support HP 3PAR StoreServ supports the VMware VAAI API, including the "block zeroing" command. Management HP 3PAR StoreServ arrays provide alerts for specific thin provisioning space issues. Alerts are issued based on pre-defined thresholds and enable efficient monitoring of capacity in thin environments. Edison: HP Thin Technologies Comparison Page 5

10 Competitive Analysis EMC VMAX Symmetrix VMAX, EMC's flagship enterprise storage platform, is the first enterpriseclass storage product to move away from custom hardware design. It uses commoditybased Intel processors with customized hardware managing the interconnect between storage modules. The VMAX operating system Enginuity is an evolution of the code developed for the first Symmetrix ICDA (Integrated Cache Disk Arrays) in 1991, and it still retains many of the original architectural design features and constraints. The discussion of VMAX in this section covers the latest 10K, 20K and 40K models. Background Thin provisioning in VMAX is implemented as a feature called Virtual Provisioning EMC's brand name for their thin provisioning technology. Thin provisioned LUNs are known as thin devices and take physical storage from thin pools. A thin pool is created using standard "thick" LUNs (termed data devices), which are subdivided into allocation units called thin device extents. Thin pools must use the same emulation and RAID protection type and EMC recommend building them from disks of the same rotational speed and data device size. A thin extent is 12 tracks or 768KB in size and represents both the initial minimum assigned to all thin devices when they are bound to a thin pool and also the lowest increment of granularity when the capacity of a thin device is extended. HP 3PAR StoreServ thin technology uses the much smaller increment of 16KB, which results in less wastage, particularly with fragmented and thin-hostile file systems. Thin devices are effectively cache-based objects that simply reference the underlying physical pool of standard LUNs in array. These LUNs in turn, map to physical disks. A single VMAX system supports up to 512 pools and 64,000 thin devices. HP 3PAR StoreServ Comparison Start Thin VMAX Virtual Provisioning requires a significant amount of initial planning. EMC recommends the use of large data devices within pools. As data devices are effectively standard LUNs, typical configurations create LUNs to be used purely for thin pools and LUNs to be used for non-thin provisioned usage. Meta devices (a linked series of multiple standard devices) cannot be used as data devices. This practice leads to waste and a shortage of the right type of storage. It is possible to dissolve and resize standard LUNs, however the process is time consuming and can lead to unbalanced performance. Edison: HP Thin Technologies Comparison Page 6

11 With HP 3PAR StoreServ thin technology, physical disks are simply assigned to a pool from which either thin or thick LUNs can be provisioned. When VMAX thin devices are bound to a thin storage pool, a minimum allocation of one thin extent (768KB) is reserved. As thin devices are effectively cache objects, each device consumed an additional 148KB of cache, plus 8KB per 1GB based on the size of the thin device. With HP 3PAR StoreServ thin technology, no initial space reservations are made. HP 3PAR StoreServ Comparison Get Thin There is no functionality within the VMAX array to optimize storage when converting thick LUNs to thin devices. As thick LUNs are copied to a thin device, the space occupied by the thin device is 100 percent of the logical allocation. Thin devices must be optimized, using a process called Space Reclamation. This means data migrations moving thick to thin LUNs require additional physical capacity to be available for the migration process. HP 3PAR StoreServ thin technology uses the Thin Conversion feature to optimize the migration of thick to thin LUNs in real time at line speeds. HP 3PAR StoreServ Comparison Stay Thin EMC VMAX arrays are able to reclaim "empty" or zero pages of a thin device using Space Reclamation. This runs as a background task on the Disk Adapter associated with the LUN. An entire thin extent is read into cache and examined, checking the T10-DIF values for each block of data against a known T10-DIF value for an all-zeros block. If the entire thin extent contains only zeroed data, then it is released from use. Until the space reclamation process is run, any zeroed areas of a thin device still consume physical space. VMAX space reclamation cannot be used with thin devices that are in an active SRDF (Symmetrix Remote Data Facility) pair or are using local replication. With 3PAR StoreServ thin technology, the process of zero-detecting is done inline using a custom ASIC. This has no impact on the controller processor or cache utilization levels and occurs in real time at line-speed. There are no restrictions on replicated LUNs. VMAX Restrictions EMC recommends a utilization level of between percent per thin pool in order to prevent "out of space" issues. With multiple pools (which are required for different RAID data protection types) this can result in significant waste. HP 3PAR StoreServ thin technology does not require separate pools for multiple protection types. When using Synchronous SRDF with VMAX, only one active write is permitted per thin device. Where thin devices are created into meta-devices, this can result in a performance impact. There is also a limit of eight read-requests-per-paths for each thin device, which can result in slow performance with high read miss rates. Edison: HP Thin Technologies Comparison Page 7

12 NetApp NetApp storage appliances were originally developed to deliver network-attached storage using either the CIFS or NFS protocols. Over time, NetApp have developed their platform to cater for block storage, using either iscsi or Fibre Channel. The current versions of NetApp filers can be configured in either 7-mode or cluster-mode and represent two distinct product lines based on the original Data ONTAP operating system, and the codebase from the acquisition of Spinnaker, Inc., respectively. Background NetApp filers implement block-based storage within Data ONTAP by emulating LUNs within volumes known as FlexVols. FlexVols are then created on aggregates (pools of physical storage) and physical disk RAID groups. The underlying architecture uses a data layout called WAFL (Write Anywhere File Layout) that operates a "write-new" policy for both new data and updates; no block or file data is ever updated in place. WAFL uses a page size of 4KB, storing updates in non-volatile RAM before writing an entire "stripe" of data to disk. In this way, writes are optimized on commit-to-disk using a RAID-4 physical disk configuration. NetApp LUNs are emulated through files on volumes; therefore, both block and file data can be mixed within the same storage pool. LUN creation is a simple process to achieve, however the use of block-based LUNs involves significant complexity. HP 3PAR StoreServ Comparison Start Thin All NetApp volumes by default are "thick" provisioned with thin volumes simply having a no space guarantees. In turn, LUNs within a volume are thin provisioned if they have space reservation disabled. By default, all LUNs are thick provisioned and have space reservation enabled. The administrator must turn off space reservation after the LUN is created to make it thin-provisioned. However, as blocks of data are not overwritten in place, an additional amount of space (called Fractional Reserve or Overwrite Reserved Space) must be reserved to manage data updates where snapshots are used on the LUN. By default Fractional Reserve is set at 100 percent when the space guarantee is set to "file" for a volume. This is the only way to guarantee enough space is available within the volume to hold updates to the entire contents of the LUN. Space guarantees are complex and if used incorrectly can result in LUNs going offline in order to protect data. The system creates a propensity to over-configure storage in order to reduce the risk of data access issues. HP 3PAR StoreServ thin technology is implemented in a much simpler way and does not have the management complexity seen in the NetApp platform. Edison: HP Thin Technologies Comparison Page 8

13 HP 3PAR StoreServ Comparison Get Thin NetApp has no native features for importing LUNs from other storage platforms. LUNs migrated into the NetApp platform using host-based tools allocate physical space matching the entire logical size of the LUN. There are no native features within Data ONTAP to identify and reclaim zero or empty pages of data. Data ONTAP does implement data deduplication (called dedupe) at the block level, and it is possible to use this feature to deduplicate zeroed pages of data. However there are restrictions on the size of LUNs that have dedupe enabled. In addition, deduping can have negative performance impacts on highly utilized LUNs. NetApp quote tests that show the performance impact for writes on deduplicated volumes becomes worse with larger systems; for example the FAS6080 can have a performance degradation of up to 35 percent. HP 3PAR StoreServ thin technology has no performance impact. HP 3PAR StoreServ Comparison Stay Thin Over time, as data is written to a NetApp block-lun, the physical space used trends towards the logical LUN size. There are no in-built features for enabling zero-block identification and reclaiming. Instead, NetApp requires the deployment of a host-based agent called SnapDrive to track updates to the file system. The agent must be deployed on every server to which NetApp LUNs are presented; otherwise the tracking of file deletions cannot occur. Platform support for SnapDrive is limited and does not include common operating systems such as RHEL6. HP 3PAR StoreServ thin technology automatically detects zero-block data inline with no performance impact and does not require the implementation of host agents. Hitachi VSP The VSP is Hitachi's current enterprise-level storage array and is the evolution of previous Lightning and USP-V models. The VSP retains the use of custom ASIC technology, in which the management of storage processes is handled by Virtual Storage Directors connected to the back-end switch matrix. Custom ASIC usage has been a feature of all of the Hitachi storage platforms; however it isn't used directly in the thin provisioning approach or in managing the efficiency of thin provisioned storage. Background VSP thin provisioning technology is known as HDP--Hitachi Dynamic Provisioning. HDP thin LUNs (called LDEVs or logical devices) are created from a HDP pool that comprises standard LDEV devices. In turn, LDEVs are created from RAID groups, built from up to 16 disks in one of seven RAID-5 or RAID-6 variations. At the physical level, data is written in tracks of 256KB per physical disk, which results in a standard logical Edison: HP Thin Technologies Comparison Page 9

14 page size of 42MB, in order to accommodate all possible RAID levels. This means initial volume allocations and volume expansion of thin LUNs is in 42MB-page increments that can result in inefficient use of space with small file block size and thin-unfriendly file systems. With HP 3PAR StoreServ thin technology, space allocations are made in 16KB increments, which results in much less wastage in thin-unfriendly environments. HP 3PAR StoreServ Comparison Start Thin The creation of VSP HDP pools requires considerable planning. Hitachi recommends that pools be created using large LUNs built from traditional RAID groups. RAID group creation is typically performed at array installation time and so is a one-off task. The RAID group size depends on how many physical disks and back-end directors have been installed within the VSP. However it is normal to build HDP pools from many RAID groups across all back-end directors to ensure maximum I/O performance so called wide striping. Although standard "thick" LDEVs can be created from the same RAID groups used to create HDP pools, for performance reasons, the practice isn't recommended. The implementation of HDP can result in wasted resources and always requires the reservation of many RAID groups to thin provisioning. By contrast, with HP 3PAR StoreServ thin technology physical disks are simply assigned to a pool from which either thin or thick LUNs can be provisioned. On VSP, thin LDEVs allocate a minimum of one 42MB page on assignment to an HDP pool. With HP 3PAR StoreServ thin technology, no initial space reservations are made. HP 3PAR StoreServ Comparison Stay Thin The Hitachi VSP platform enables traditional "thick" LUNs to be imported into the system using the external virtualization feature of the array, known as Universal Volume Manager. In addition, "thick" LUNs can be imported from other VSP systems using TrueCopy replication. Any imported LUNs remain fully allocated at their original logical size until zero-block reclaim is performed using the zero-page-reclaim feature. ZPR is a post-processing background task that examines individual LDEVs and releases 42MB pages back to the HDP pool. Hitachi recommends ZPR be executed during periods of inactivity, as the task is performed by the back-end directors and can have a performance impact on production I/O. As ZPR is not performed in-line, thin LDEVs will "grow" over time as data is written to the file system on the LUN. This means thin pools need to be provisioned with additional capacity to cater for this growth between ZPR reclaim tasks. With 3PAR StoreServ thin technology, the process of zero-detection is done inline using a custom ASIC. This has no impact on the controller processor and occurs in real time at line-speed. Edison: HP Thin Technologies Comparison Page 10

15 EMC VNX EMC's VNX platform is an evolution of the previous CLARiiON and Celerra products (serving block and file protocols respectively). The two platforms were brought together and marketed as a single platform, using one management tool, called Unisphere. Blockbased storage LUNs are presented from the base hardware unit, with file access implemented on x-blade modules. Thin provisioning technology is implemented using the Virtual Provisioning (VP) feature. VP extends the capabilities of LUN configuration to include both thick and thin LUNs on the same disk pool. VP disk pools can be comprised of large numbers of disks (greater than the standard disk pool which is limited to 16 devices), but still configures disks in RAID groups for resiliency. HP 3PAR StoreServ Comparison Start Thin VNX thin LUNs can be logically defined in sizes from 1MB to 16TB. However each LUN reserves a minimum of 3GB. This means allocation of a large number of LUNs has a significant reservation on physical space, in contrast to HP 3PAR StoreServ thin technology s no minimum physical spare reservation. HP 3PAR StoreServ Comparison Get Thin VNX does not support any native inline zero-page reclaim functionality. Instead, "empty" pages must be reclaimed by using either the LUN Migration (within the array) or SAN Copy (from external arrays) functions. This means that thin LUN physical capacity will trend towards their logical size over time. EMC recommends using the sdelete host command and LUN migration as the method of reclaiming unused space in the VNX array. By comparison, HP 3PAR StoreServ thin technology detects and eliminates zero-page data inline with no need to perform additional manual data migrations. VNX supports the Symantec Thin Reclamation API, however this requires the deployment of the Veritas File System on every server for which reclaim is required. HP 3PAR StoreServ Comparison Stay Thin VNX thin LUNs grow in increments of 1GB of physical space, with 8KB blocks used as the minimum level of granularity. The 8KB block refers to the space within which zero page data can be reclaimed, however each increment of space assigned to a LUN works in steps of 1GB, so any 8KB holes "punched" out of a 1GB slice can only be reused by that volume, rather than as free space for all available volumes. HP 3PAR StoreServ thin technology implements LUN mapping to internal logical disks at 32MB pages, with 16KB representing the minimum level of page granularity for thin provisioning. This makes the 3PAR system much more efficient with thin LUNs. VNX has no ASIC technology to perform inline zero space reclamation, unlike HP 3PAR StoreServ. Edison: HP Thin Technologies Comparison Page 11

16 Performance Considerations EMC highlight that Virtual Provisioning Thin LUNs do provide more flexibility, but offer lower performance than traditional thick LUNs and so recommend their use only for applications requiring "moderate" performance. HP 3PAR StoreServ thin technology has no performance restrictions. IBM XIV The IBM XIV storage array platform was acquired from an Israeli startup, founded by the inventor of the EMC Symmetrix, Moshe Yanai. The platform takes a radical departure from traditional arrays and uses only high-capacity SATA or SAS hard drives, although the configuration has recently been expanded to accelerate I/O using an SSD cache layer. XIV is now at the third generation of hardware, utilizing either 2TB or 3TB drives, with 6TB of SSD cache. Each array is comprised of between six and 15 server nodes, which hold 12 hard drives each, resulting in a maximum configuration of 180 drives. Each node subdivides disks into 1MB chunks, which are then distributed across all disks as a single large pool of mirrored data. XIV uses the terms "soft size" and "hard size" to refer to the logical and physical size of a LUN respectively. These terms also apply equally to pools that can be allocated physical capacity. It is possible for a pool to deplete hard (physical capacity) and lock access to a volume, despite there being free physical space in other pools. The overall capacity of an XIV array is referred to as the "system hard size." A "system soft size" the degree of over-provisioning permitted at the array level is also defined, but can't be modified by the system administrator. This value has to be set by an IBM engineer and requires the customer to indemnify IBM against any issues that occur as a result of the change. HP 3PAR StoreServ Comparison Start Thin By default, all XIV LUNs are thin provisioned and placed into storage pools. As data is spread equally across all drives in the system, storage pools provide no more than a logical administrative benefit for thin provisioning; no workload segregation is possible. Due to the architectural design of the system, all LUNs reserve an initial 17GB at creation time, which can result in a significant initial waste of space. In addition, all LUNs are incremented in 17GB chunks. HP 3PAR StoreServ thin technology reserves no space on initial LUN creation, and uses increments in 16KB, making it highly efficient. HP 3PAR StoreServ Comparison Get Thin XIV can support the thick-to-thin conversion of volumes as part of the Data Migration feature. Volumes imported from other systems do have zero-pages identified and removed during the process. However, Data Migration requires configuration changes Edison: HP Thin Technologies Comparison Page 12

17 and the placement of the XIV "inline" with the host and the original volume. This task requires an outage to achieve. With HP 3PAR StoreServ thin technology, data can be migrated into the array via the host, identifying zero-pages in line and without requiring a host outage. HP 3PAR StoreServ Comparison Stay Thin XIV implements a zero-page-reclaim feature to identify and eliminate "empty" blocks of data. However, the feature is implemented as part of the background data "scrubbing" routine that trawls the array and looks for data integrity and parity issues. Reclamation of ZPR data can take many days (or as long as three weeks) to complete, so there is an over-allocation of physical space until zero pages can be identified and recovered. HP 3PAR StoreServ thin technology implements active ZPR detection inline at the time of data write, ensuring "empty" pages are immediately identified and eliminated before data is written to physical disk. XIV supports the Symantec Thin Reclamation API for instant space reclamation, enabling hosts running Symantec Storage Foundation, version 5 and above, to directly signal to the array when storage is released. This requires the deployment of the Veritas File System on each host connected to the array. Instant space reclamation does not support mirrored volumes, volumes that have snapshots or snapshots themselves, making the recovery process limited. Edison: HP Thin Technologies Comparison Page 13

18 Testing Overview and Methodology The aim of performing vendor comparison tests is to show how HP 3PAR StoreServ compares to other vendors in terms of performance and efficiency. Although the implementations from each vendor appear to offer similar features, the implementations differ greatly in their performance and efficiency. The following tests were performed in the competitive summary list. The storage systems tested were not directly comparable for performance targets or specifications. They varied in the number, size and types of drives, the number of controllers and other physical specifications. Therefore, the data generated in Edison's zero-page-reclaim performance test should only be compared for the differences for each tested array from the test baseline. The exception is the Large Pre-Allocation results, which demonstrate the effects of the different thin provisioning and storage architectures on capacity utilization, rather than a change in performance for the systems. Details of the hardware tested can be found in the Appendix, at the end of this document. Test 1 Zero-Page-Reclaim Performance This test aims to show the impact of zero-page-reclaim functionality on each array. The reclaim function is an essential property of "stay thin," ensuring that ongoing allocations don't turn thin volumes into thick ones over time. Ideally this test should not impact I/O performance. The test process performed the following steps: 1. Create a single large "thick" 200GB LUN and assign to a Windows host. 2. Quick format the LUN with the NTFS file system. 3. Perform load test with IOMETER, writing binary zeros to the LUN, recording IOPS and latency figures. 4. Repeat the test with a 200GB thin LUN. Prior to the test, the zero-page-reclaim task was enabled on the VSP system. For the EMC platforms, the zero-page-reclaim feature was enabled by performing a LUN migration, the method recommended by EMC. Edison: HP Thin Technologies Comparison Page 14

19 Test 2 Large Pre-Allocation This test aims to show the overhead at the initial creation of thin LUNs and addresses the requirement to "start thin." Ideally the creation of thin LUNs should reserve the minimum amount of storage possible on the array. The test process performed the following steps: 1. Create five 200GB thin LUNs and assign to a Windows host. 2. Quick format the LUNs with the NTFS file system. 3. Measure the amount of space consumed as indicated by the array. Edison: HP Thin Technologies Comparison Page 15

20 Test Results Test 1 Zero-Page-Reclaim Performance The data in these tables represents the performance for each array capable of zero-pagereclaim within the test parameters. Data for IBM XIV was not included because that system performs reclaim over a very long period of time that was outside the test parameters. 1 Platform Degradation from Baseline (%) EMC VMAX 48.19% Dell Compellent 42.33% EMC VNX 29.99% Hitachi VSP 23.34% HP 3PAR 0.00% Table 1 - Test 1 - IOPS Performance during ZPR 1 According to an IBM Redbook, IBM XIV Storage System: Copy Services and Migration, it, "could take up to three weeks for used space value to decrease This is because recovery of empty space runs as a background task."(page 264). Not only is the time required for ZPR outside the parameters of our research, enabling over-provisioning is, "not within the scope of the administrator role."(page 30) This suggests that an IBM engineer must perform an overprovisioned configuration. Edison: HP Thin Technologies Comparison Page 16

21 Figure 1 - Test 1 - IOPS Performance during ZPR Platform Degradation from Baseline (%) EMC VNX 42.61% EMC VMAX 40.58% Dell Compellent 74.22% Hitachi VSP 30.33% HP 3PAR 1.23% Table 1 - Test 1 - I/O Latency during ZPR Edison: HP Thin Technologies Comparison Page 17

22 Figure 2 - Test 1 - I/O Latency during ZPR The results of this test show that ZPR activity has an impact on both the latency and throughput of each platform except HP 3PAR StoreServ. The greatest effect was seen on EMC VMAX performance and the latency increase with Dell Compellent. Edison was able to determine that performance impact shown on EMC VMAX was because the platform needs to read each thin device extent into cache in order to perform ZPR processing. This cache load clearly has a direct impact on array performance. Edison was unable to diagnose the causes of the increase latency on the Dell Compellent system. The HP 3PAR StoreServ array has dedicated ASICs to handle the ZPR workload without impacting on delivering I/O to hosts. Edison: HP Thin Technologies Comparison Page 18

23 Test 2 Large Pre-Allocation The results from this test are shown in the following table and graph. Platform Space Allocated (MB) EMC VMAX 17 NetApp FAS 368 Dell Compellent 800 Hitachi VSP 1,230 HP 3PAR 3,125 EMC VNX 20,039 IBM XIV 86,000 Table 2 - Test 2 - Large Pre-Allocation Figure 3 - Test 2 - Large Pre-Allocation Edison: HP Thin Technologies Comparison Page 19

24 The results of this test show EMC VNX and IBM XIV performed poorly in preallocations. EMC VNX reserves a minimum of 3GB per LUN; IBM XIV reserves a minimum of 17GB per LUN. The other platforms performed well. Clearly when systems have large volumes of LUNs, the minimum reserve can have a detrimental impact on the aims of "starting thin," resulting in large amounts of unusable storage. Edison: HP Thin Technologies Comparison Page 20

25 Conclusions and Recommendations Thin provisioning is a great space optimization feature that can be used to increase levels of utilization on storage arrays. The direct benefit is reducing capital expenditure on hardware and operational expenditure on management. However as we have seen from the tests, not all thin provisioning implementations are equal in terms of their ability to optimize space with minimal impact on performance. HP 3PAR StoreServ systems adhere to three basic principles: 1. Start Thin the creation of new LUNs requires minimal overhead. In Test 2 we saw all arrays perform efficiently at this, except for the EMC VNX and IBM XIV platforms. With low overhead on LUN creation, the efficient platforms can scale to far greater numbers of LUNs and so can deliver storage resources more efficiently. 2. Get Thin the ability to move data from thick to thin deployments. The import of existing data into an array requires features that enable data to be optimized as it is written to disk. Only HP 3PAR StoreServ is able to perform inline zero detection at write time. EMC VNX, Dell Compellent and IBM XIV are able to zero detect when data is imported under certain circumstances, for example as part of replication, but these are not completely flexible solutions. 3. Stay Thin the ability to detect and free unused space over time. As data is written to thin volumes, the trend is for LUNs to grow in size to equal the logically allocated capacity. This can happen because of defragmentation or with "thin unfriendly" file systems that embed metadata with content, or are inefficient at reusing released resources. Most vendors, with the exception of NetApp now support some form of zero-page-reclaim or UNMAP feature, where space is returned to the array when released by the host. However these background tasks can have a significant impact on host I/O performance as was demonstrated in Test 1. Only the HP 3PAR StoreServ platform provides a thin provisioning implementation that delivers the most efficient storage utilization. Best Practices The testing and research in this white paper highlights a number of best practice considerations: 1. Implement Zero-Page-Reclaim This feature should be used to ensure LUNs stay thin, however on most platforms (except 3PAR because of its custom ASIC and XIV Edison: HP Thin Technologies Comparison Page 21

26 because it runs so slowly) needs to be scheduled out of normal production hours to minimize performance impact. 2. Be aware of minimum LUN sizes When setting a standard for thin provisioned LUNs, ensure that the minimum configured LUN size is not likely to waste capacity. Edison: HP Thin Technologies Comparison Page 22

27 Appendix A Document References The following documents were referenced during the production of this white paper. TR NetApp Deduplication for FAS and V-Series Deployment and Implementation Guide TR-3563 NetApp Thin Provisioning Increases Storage Utilization with On Demand Allocation TR-3483 Thin Provisioning in a NetApp SAN or IP SAN Enterprise Environment GC IBM XIV Storage System Planning Guide GC IBM XIV Storage System Product Overview 4AA3-3516ENW HP 3PAR Architecture Best Practices for Fast, Simple Capacity Application with EMC Symmetrix H EMC VNX Virtual Provisioning White Paper EMC VNX Series Release 7.0 VNX System Operations Dell Compellent Data Progression Data Sheet Edison: HP Thin Technologies Comparison Page 23

28 Appendix B Test Equipment Specification The following equipment was used to perform the testing documented in this white paper. Arrays Hitachi VSP NetApp FAS3140, running Data ONTAP 8.0.2, RAID-DP across 28 drives. Dell Compellent RAID-5 across 72x 600GB SAS drives EMC VNX5700 running microcode 5.31, RAID-5 across 24x 300GB 15K SAS drives. HP 3PAR F400 InForm OS (MU1) EMC VMAX-20K IBM XIV Gen2, 72x 1TB SATA drives Servers HP BL Blade Servers, 2x Intel X5650 CPU, 16GB RAM, HP Flex10 I/O Windows 2008R2 SP1 & CentOS 6.2 IOMeter v AA4-4079ENW Edison: HP Thin Technologies Comparison Page 24