Best practices for IT Storage Consolidation. How IP SAN and VMware are changing the IT Landscapes. White Paper. virtualized by

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1 Best practices for IT Storage Consolidation How IP SAN and VMware are changing the IT Landscapes White Paper virtualized by

2 The Evolution of Resource Sharing The management of IT has become more and more refined as time passes. We have gone from an age of throwing big iron and expensive solutions at any problem to a more focused approach which emphasizes selecting, installing and deploying the most productive and cost efficient tool for a given situation. As the traditional environment of Direct Attached Storage (DAS) connected to many separate physical servers has proven to be expensive, difficult to scale, and most of all, very resource intensive to manage, IT professionals have sought out new, innovative ways to more effectively put the two workhorses of any IT environment - servers and storage - to better use. Several technologies have evolved that facilitate the pooling and sharing of server and storage resources. While discrete islands of technology still exist in many enterprises, the concept of networked resources and virtualization continues to gain ground in these same environments. One of the key storage technologies that have evolved is Storage Area Networks or SANs. SANs, which facilitate the sharing of storage resources in a networked environment, provide an effective solution to storage management. By facilitating the sharing of a centrally managed pool of storage, end users can often consolidate their discrete islands of storage and gain significantly improved utilization of their systems. When SANs first appeared on the market in the late 90s they all used Fibre Channel (FC) network technology. While this is an excellent, high performance technology, FC SANs have proven to be very costly to initially deploy and very complex to manage. Consequently, only large enterprises with experienced IT staffs have deployed FC SANs. One of the earliest technologies that were developed to enable resource sharing was Ethernet. As the internet evolved into a mainstream IT tool, product developers saw the opportunity to take the underlining Ethernet protocol, internet Small Computer Systems Interface (iscsi), and adapt it for a networked storage environment. The first iscsi based SANs were introduced to the market in mid This technological breakthrough made networked storage affordable to all end users ranging from small and medium sized businesses (SMBs) to large enterprises. Initially, the performance and bandwidth of this technology was limited as compared to FC SAN. However, now we have 10 Gigabit per second (Gbps) based IP SANs available, and for the first time, the bandwidth of Ethernet surpasses the bandwidth of FC storage networks. Once the initial resource sharing technologies started to gain ground, the next challenge that arose around solutions that reduce the cost and complexity of the IT environment was how to manage the exploding number of small servers that were being supported with networked storage. In the same way that managing independent storage islands became costly and unwieldy, managing a large number of servers attached to the same SAN, also, became a significant undertaking. Deploying a uniform operating system environment and application implementation accessing the shared, centralized SAN now became an imperative. This laid the foundation for a movement toward sharing server resources in a centralized manner. And, as more and more servers were consolidated through server virtualization, the need for corresponding storage consolidation grew more compelling. Although virtualization s direct impact on overall storage demand is modest, it will accelerate the shift from direct attached to networked storage, wrote analyst David Bailey, highlighting increased iscsi deployments. With VMware s latest enterprise package, Virtual Infrastructure 3 [VI3], NAS and iscsi solutions are now more viable options. With the availability of 10Gb connectivity between physical servers and storage, server, storage and network consolidation has become a reality and not just a dream.

3 Data Center Operational Challenges The development of the resource sharing technologies discussed above is just the first step in meeting the day to day management and operational challenges of enterprise data centers. The next set of challenges that need to be mastered are rising costs, server and storage under utilization, network congestion and complexity, manageability and efficiency. Rising cost and under utilization: Once you get past the initial cost associated with purchasing new equipment, there are several other categories of cost that take on increasing importance in a typical data center. They include the costs associated with electrical power, floor space, cooling and management. In some data centers, energy costs have reached 30% of their total operational budget. Many organizations see server and storage consolidation as an effective way to tackle and reduce these costs. While there has been some movement toward sharing of server resources, many companies still deploy many separate physical servers for various applications. Most organizations have recognized that maintaining racks of separate servers that consume more physical space and more power has become too expensive. These server costs have further exacerbated the significant underutilization that is rampant in data centers. The typical utilization rate is only 30%. Server virtualization technologies address this problem and are growing in popularity. Network congestion and complexity: One area that is sometimes overlooked when doing the physical consolidation is the network congestion that can result. While it may seem obvious, it is easy to overlook the fact that the consolidation of the systems does not lessen the amount of data flowing over the network. Data from all the consolidated servers have to go through a single physical server. In the consolidated environment, it is not surprising to see single server loaded with 20 NICs or more; this is exactly where 10Gb Ethernet can help. By deploying 10Gb Ethernet, you can reduce rack space as well as the amount of cabling and floor space. A single dual port 10Gb NIC can replace 20 1Gb NICs without any performance degradation, while offering better link utilization. Ethernet is not only a server to server communication technology; it is also a server to storage communication technology. Many different communication technologies have been deployed in the data center over the years including Ethernet, Fibre Channel, Infiniband, etc. With 10Gb Ethernet IP SANs, you can create a unified networking environment that will work well with your server consolidation project and reduce network complexity at the same time. Manageability and Efficiency: In addition to network congestion and complexity, an increase in server sprawl can generate additional time consuming management tasks such as server provisioning, configuration, monitoring and maintenance. As the number of servers grows, the task of managing servers becomes increasingly complex. Addressing the manageability challenge is another key factor that is driving organizations to consolidate their server and storage resources. When you consolidate these resources, you significantly decrease the number of unique assets that have to be managed separately. If you also increase the utilization of each individual asset, you can also reduce the number and size of the equipment footprint. This in turn reduces the use of floor space and power.

4 Technical Insights into storage consolidation with iscsi and FC Through the deployment of a FC or IP SAN, you can virtualize storage, and provide storage services to the host servers through either an IP or FC network. The underlying disk subsystem is almost identical. It is interesting to note that many storage systems in the market today offer both IP and FC interfaces. Many of the features offered on FC SAN are now also offered on IP SAN. The Internet Small Computer Systems Interface (iscsi) is a protocol that transports SCSI commands and data over a TCP/IP network as specified in RFC iscsi transport I/O from a host [initiator] to iscsi storage system [target] over the IP network, leveraging standard network equipment. The network can be 10/100/1000 or 10Gb based. Nodes are connected to the network via a standard IEEE network interface card (NIC) or an iscsi host bus adapter (HBA). An iscsi HBA has a TCP/IP offload engine (TOE) that manages the TCP/IP overhead; as a result CPU cycles are not used for TCP/IP packet processing. Jumbo frame support can also reduce the number of server CPU cycles utilized. FC SAN is a networking oriented SAN architecture. In order to manage the flow of data between storage and servers around the network, provisioning a FC SAN requires that an FC switch be properly configured through technology known as zoning. Zoning establishes routing between FC switches, servers and storage on an FC SAN. On the other hand, an IP SAN is network transparent because it uses the common IP addressing for all routing. Because SAN provisioning doesn t require reconfiguring an IP switch the administrator can focus their attention on the storage rather than being hobbled with new and intricate networking concepts. Guidelines for choosing SANs The next few sections compare the rationale for choosing a FC or IP (iscsi) storage configuration for different situations. Table 1 summarizes the major differences. Table 1 Summary of FC and IP SAN Difference Performance Manageability Security Cost FC 1Gb/2Gb/4Gb Difficult Good High IP SAN 1Gb/10Gb Easy Good [VLAN, CHAP, IPSec] Low

5 Performance: This is perhaps the more common technical issue that is raised when discussing the merits of IP SAN. When you look at performance, it is important that you consider not only the size of the transport pipe, but also the characteristics of the applications that the storage is supporting. For example, most people would assume that FC s 4Gb bandwidth is four times faster than Ethernet s (iscsi) 1Gb bandwidth and that 10Gb Ethernet would be 10 times faster than 1Gb Ethernet. While it is important to have the correct bandwidth available to meet the requirements of an application, it is also necessary to engage the proper storage for the application in order to ensure optimal performance. Often the size of the network transport pipe is not the bottleneck in the performance of many applications. This is especially true for applications that have random I/O data patterns, in which the timing and frequency of the I/O is more important than the actual size of data (which tends to be small). In a high I/O transactional environment, it is the read/write performance of the hard disk drives that cause the performance bottleneck, not the available network bandwidth. On the other hand, for applications that use sequential I/Os, such as backup to disks and streaming data, the performance bottleneck is mostly tied to the available bandwidth. In a large data transfer environment, network performance is usually the measure of system throughput performance. In these situations, a high bandwidth iscsi SAN such as a 10Gb based IP SAN provides better performance than a 4Gb FC SAN. A Microsoft Exchange application test helps illustrate these differences. This test which tested and qualified both an IP SAN and FC SAN used the Microsoft Jetstress tool. In one test, with 128 SATA II drives, an Intransa 10Gb IP SAN was successfully tested in a 10,000 user environment. The 10,000 user limit was due to the number of disk drives tested rather than the available bandwidth of the pipe. One of the performance attributes tested in this scenario was the checksum speed that Exchange exhibits when it undergoes a data integrity test. In this test, the Intransa 10Gb IP SAN achieved a speed of over 700 MBps [MegaByte per second]. This speed is more than twice the speed that was measured for the 4Gb FC system, and this is one of the advantages of 10Gb IP SAN. A corollary issue that is tied to performance of the SAN network is network latency. From a pure network latency point of view, one of the major factors that affects response time is the network serialization delay, or the impact on transmission time that is caused by limited network bandwidth; this is especially true for a large size data request. For example, the transmission time for a 512KB request, is 4.2ms with a 1Gb link versus the much faster 0.42ms if you use a 10Gb link. Improved response time due to decreased network latency is another advantage of 10Gb when evaluating the performance of IP SANs. Manageability: As discussed earlier in this paper, another major issue in most data centers is manageability. Earlier we focused on server manageability. Here we are focusing on the ability to easily deploy, run and maintain a SAN. Familiarity with the base technology of IP SANs is a key reason it is gaining popularity in enterprise and mid-size data centers. Many IT staffs are more familiar with Ethernet than with FC. Because iscsi utilizes standard Ethernet, many IT staffs prefer iscsi than FC. Assigning or presenting virtual disks to the hosts for these staffs is easier for an IP SAN than for a FC SAN. One of the reasons for this is that there is no zoning requirement with IP SANs as all addressing is IP addressing (point to point). Both FC and iscsi offer remote boot which allows servers to boot from the SAN where the OS images are located within the SAN. Because booting from a SAN eliminates local hard drives, it facilitates centralized management of the OSs as well as application data. Therefore you can achieve rapid boot image cloning and fast server provisioning, reduced complexity and risk, and better data security because all data, including OS images are managed at the SAN rather than at each desktop or server. For desktop remote boot, it would be very costly to have FC HBAs on every desktop.

6 Security: While security of an organization s data has always been very important, it has grown even more in importance as internet fraud escalates and new compliance regulations are enacted. A very common misperception is that IP SANs are not as secure as FC SANs. However, there are several approaches a data center can take to make their iscsi environment much more secure. One way to do this is to separate your iscsi neteworks logically or physically. If you do this, an IP SAN can be just as secure as a FC SAN. If your iscsi network runs on a shared corporate data network, you can secure your iscsi data from unwanted access by implementing virtual LANs (VLANs) For very security-conscious customers; you can deploy the Challenge Handshake Authentication Protocol (CHAP). CHAP is an authentication protocol that defines a methodology for authenticating initiators and targets. Almost all IP SAN vendors support CHAP. To provide further data security, users can choose IPSec for data encryption. High Availability: Of course, facilitating the availability of your data to your end users is one of the most basic goals of any data center. A key strategy for avoiding any unnecessary downtime is to avoid single points of failure. One way to do this is to deploy storage systems with redundancy designed in; particularly those that provide automatic failover should any single component fail. Most current IP SAN systems build in redundancy by offering active-active dual controller configurations. Some vendors, such as Intransa, even offer up to four active-active controllers in a single storage system configuration. Multipathing or the ability of a system to use more than one path to read/write data to the storage device is another high availability solution that provides fault tolerance against single point of failure. Multipathing can also provide load balancing of I/O traffic, thereby improving system and application performance. Multiple redundant paths (MPIO) Technology has been offered by Microsoft Windows iscsi initiator since Linux provides MPIO support through both NIC teaming and dm-multipath; open-iscsi has added multipath capability in its latest release. VMware has been offering NIC teaming support since version 2.5. Keep in mind that NIC teaming, such as link aggregation (IEEE 802.3ad) uses several interfaces to spread traffic, but the packet distribution rules are made so that all packets related to a given TCP connection go through the same link. Although a single TCP connection cannot benefit from this in terms of performance, multiple TCP connections can take advantage of multiple NICs and10gb based Ethernet. In the latter scenario, you will see a significant increase in performance per connection. Cost: As we discussed earlier, cost reduction is an ongoing challenge for every IT organization. The cost effectiveness of IP SAN, combined with the emerging 10Gb Ethernet technology, represents a very compelling reason for end users ranging from SMB to Enterprise to choose an IP SAN. iscsi is a cost effective and reliable choice because it runs over the low cost Ethernet infrastructure and recovers easily from transmission errors. In contrast, FC requires an expensive networking infrastructure built around FC switches and host bus adapters (HBAs). A typical IP SAN costs about 1/3 of a FC SAN. A 1Gb NIC cost $50; a 10Gb CX4 based NIC costs around $600 while a 4Gb FC HBA costs $900.

7 How Server Virtualization Utilizes Storage? Although both iscsi and FC enables storage virtualization and consolidation, this is only part of the overall consolidation picture. In this section we will review how the server and storage consolidation technologies work together to provide the end user with a more manageable environment. Companies like VMware and Microsoft both provide consolidation technology from the server prospective. Server virtualization is an approach that enables multiple servers, called virtual machine (VM) to be hosted by a single physical server. When you combine both storage and server consolidation with a unified interfacing technology you will get more efficiency and productivity out of your consolidation efforts. In this section we will review how VMware ESX manages and utilizes storage.while VMware VI3 supports FC, iscsi as well as NFS storage, we will focus on iscsi storage. All VMs communicate through virtual IP networks. While iscsi is both a networking protocol, and a storage protocol, FC is only a storage protocol. There are two ways that VMs can access the storage: Direct Storage Access through VM s iscsi initiator and Indirect Storage Access through VMware ESX iscsi initiator as showing in the diagram below: Direct Storage Access: VMs run native OS iscsi initiator, such as Microsoft iscsi initiator or openiscsi software initiator, access storage through virtualized networking stack. Figure 1 How VMware Utilizes Storage Direct Access RDM Phisical RDM Virtual VMF S Application Application Application Application Operating System Operating System Operating System Operating System iscsi Initiator VS Switch RDM Phisical RDM Virtual VMF S iscsi/fc/nfs Storage Figure 1 shows an example of a typical network topology within a physical server in VMware environment. There are two physical NICs in this configuration, one is 1Gb based and the other is 10Gb based. To increase performance and availability, you can team together multiple network adapters. All VMs can utilize the storage through their own native OS iscsi initiators or through storage service provided by VMkernel.

8 Figure 2 Typical Network Topology in VMware Environment Indirect Storage access with the VMware hypervisor iscsi Initiator: To use iscsi software initiator, first enable the iscsi initiator, and then configure VMKernel and the corresponding service console. VMware ESX supports its own VMKernel iscsi initiator. VMware uses the VMKernel iscsi initiator to access/manage storage from ESX kernel when addressing the storage adaptor. This is the iscsi software initiator within ESX. Other methods employed are with iscsi HBAs, or FC HBAs which house their own initiators for access/manage storage in the shared SAN environment with VMware ESX. VMkernel, the software layer that manages most of the physical resources on the ESX server host, is used by the TCP/IP stack that services VMotion, NFS and software iscsi. The Service Console is required since it is responsible for initial iscsi target discovery. For iscsi configuration, you will need to provide an initiator name, and the method (described above) you will use to access the storage LUNs. In most of situations, you will only need to use the Dynamic discovery method in which you only need to provide the target IP address. For security reason, you may want use CHAP authentication. As an example, Figure 2 shows how ESX sees the storage from Intransa IP SAN.

9 Figure 3 VMware ESX View of Storage from Intransa IP SAN Once the ESX iscsi initiator discovers the storage, then VMware needs to know how the storage is to be presented to VMs. There are two methods: Virtual Machine File System (VMFS) and Raw Device Mappings (RDM). VMFS is a high performance distributed file system that provides storage virtualization optimized for virtual machines. It does automatic metadata updates through the use of on-disk locks. It is a journaling file system, has some logical volume management capability. And it does support snapshot. RDM is also a VMFS file in a VM configuration. It is a pointer from VMFS to a raw device. There are two compatibility modes: Physical compatibility RDM mode and virtual compatibility mode. Physical compatibility RDM mode passes all SCSI commands unmodified from VM to the storage. Virtual compatibility mode is that mode where VMs see a virtualized device and only reads and writes are passed on to the storage device. Best Practices for Building a Virtualized Data Center VMware offers many data management capabilities. It ranges from data backup to various high availability features. The feature list includes snapshot, VMotion, clustering, HA, DRS and VCB. They all require ESX servers to have access to a shared storage system. iscsi is an ideal technology for executing complex storage management, data protection and enabling easy VM mobility. iscsi is the preferred technology for DR and backup applications because there are no complex rezoning processes to be defined to accommodate automatic failover in the event of failure during the process. In addition, iscsi throughput performance facilitates a reduction in the time expended for execution.

10 Technical Insights into VMware Data Protection Fast Service Provisioning: Eliminate software complexity with virtual appliances; pre-built application VM. You don t need to purchase new hardware to test your application. VM snapshot: VM snapshot enables administrators to take live snapshots of the current VM. Snapshot can be used to back up the VM servers, or to run before major system updates are applied, ensuring that the VMs can be brought back to a known good state in seconds. With VMware Consolidated Backup (VCB), you can consolidate your backup and reduce cost. VMotion: VMotion is the magic behind VMware s live server migrations. It enables a VM to be moved live from one ESX host to another by migrating the control over the VM to another ESX server in the cluster. This migration is transparent to the VM. The transfer happens within few seconds. Storage Motion: Storage VMotion will do the same things for storage arrays as VMotion does for servers, it will enable you to migrate the virtual machine disk file from one storage array to another. DRS: Distributed Resource Scheduler (DRS). VMware DRS continuously monitors utilization across resource pools and intelligently allocates available resources among the virtual machines based on pre-defined rules that reflect business needs and changing priorities. When virtual machine resources are constrained, additional capacity is made available by migrating live virtual machines to a different physical server using VMware VMotion. Table 2 summarizes the functionalities support for various storage protocols. Table 2 VMware Data Management Feature Support for Storage Protocols Protocol FC Software iscsi iscsi HBA NFS DRS, VMotion, HA YES YES YES YES VCB YES YES YES NO VM Boot YES YES YES YES ESX Boot YES NO YES NO Once you decide to implement server and storage consolidation, you have many choices to make regarding what primary and auxiliary technologies to deploy. Your decision will be based on functionality, performance, scalability, easy management as well as cost. FC or iscsi: When you are trying to decide whether to use iscsi or FC for your environment, you must first determine your system and storage performance requirement. One of the key factors that you must determine is whether or not your applications are extremely latency sensitive. If they are, your assessment must include the relevant network storage system requirements. 10

11 If on the other hand, the criteria that are most important in your situation are ease of management and cost, you should determine if iscsi or FC can provide the features you require for your application. You also need to evaluate whether or not you have resources easily available to manage the system from deployment to daily maintenance to trouble-shooting. Which iscsi Initiator?: Once you have decided to implement consolidation using IP SAN, the first question you should ask is do you want VMware hypervisor to manage the storage or do you want each VM to manage storage? In other words, do you want to use the hypervisor iscsi initiator or the VM based iscsi initiator? Almost all major operating systems, including Windows, Linux, Solaris and Unix have already implemented their native iscsi initiators. Now that VMware added iscsi initiator support in the VI3 infrastructure, users face a common question: Which one should we implement? We will refer to the native OS based iscsi initiator as the Direct Storage Access as it directly accesses storage from VM level. Table 3 summarizes the pros and cons of each approach: Table 3 Pros and Cons of VMware Storage Management Technologies Category VMware ESX iscsi Initiator VM iscsi initiator Direct Storage Access VM Storage Access Method Configuration Hypervisor Storage Stack Single iscsi initiator for one physical server Quick and Easy VM creation Less LUNs to manage Hypervisor Network Stack Many iscsi initiators per physical server (one for each VM) VM-Storage Integration None Snapshot, VDS, VSS Storage Array Snapshot Multipathing NIC Teaming MPIO and/or NIC teaming iscsi HBA support Yes No VMware Consolidate Backup (VCB) Yes No With Direct Storage Access, the iscsi initiator running in the VM OS, ESX arbitrates network access. With iscsi running in the VMkernel layer, ESX arbitrates storage access, and serves as a virtual SCSI HBA to the VMs. 11

12 Based on performance evaluations Intransa did under different workloads with various number of VMs, we found that there are no significant performance or CPU utilization differences between the two scenarios. Direct Storage Access performs better in some situations, while VMware ESX iscsi initiator performs better in others. Therefore, performance should not be your major concern when choosing either of the iscsi initiator options. One of the advantages of running iscsi initiator within the VM is that it allows the system administrator to manage their VMs the same way they manage their physical servers without any data migration. The drawback is that you will not be able to take advantage of any VMware data protection options. Our recommendation is to use VMware iscsi initiator unless your deployment already has tight server to storage integration. You will only deal with one iscsi initiator per physical server, and have fewer LUNs to manage. VMFS and RDM: Once you have decided that you will use VMware ESX iscsi initiator to manage the storage, the next question you have to answer is what storage mode? There are two major modes: VMFS and RDM (as discussed in previous section). You should use VMFS for flexibility and easy management. If you have to support VM clustering, such as Microsoft Cluster Service, you will need to use the RDM mode. Table 4 summarizes the major differences between these two implementations: Table 4 Comparisons of VMware Storage Modes: VMFS and RDM Use VMFS if you Easy provisioning of VM Replicate entire VMFS volume VMware snapshots VMware Consolidate Backup (VCB) Use RDM if you Reply on SAN Replication No VMware snapshots, but reply on Storage array snapshot Clustering VMs between physical servers Online expansion at VM level using array-based expansion technology Use servers with multi-core processors: You can also achieve a level of consolidation by using servers and storage systems with higher speed Multi-core processors. Newly introduced servers with multi-core processors are an excellent consolidation platform, delivering three to five times the performance of systems that were offered just 12 to 18 months ago. 2 Dual-socket, quad-core processors represent the sweet spot for the vast majority of applications, delivering the best priceperformance value in rack-mounted or blade servers. Use high speed interconnecting technology such as 10Gb Ethernet. An approach that is gaining in popularity is the use of all Ethernet connectivity for your entire environment, from servers to servers, and servers to storage. With 10Gb Ethernet, you can significantly reduce the thousands of cables, rack space and power usage in your data center. 10Gb Ethernet also supports more VMs on a single physical server without worrying about bandwidth limitations. Conversely, deploying virtual server technology with traditional FC SANs requires specialized switches, adapters and expertise. 12

13 Table 5 shows the power consumption from a connectivity point of view; it is interesting that Dual 10Gb NIC transports more bits per Watt than rest of NICs/HBAs listed here: Table 5 Power Consumption of Different NICs and HBAs Power Consumption (Watts) Gigabit per Watt 1Gb NIC Dual 1Gb NIC Gb NIC Dual 10Gb NIC Gb FC HBA Dual 4Gb HBA By implementing a SAN that uses IP Ethernet based technology, you have an opportunity to unify your communication and storage networking technology. With a unified IP Ethernet transport, you can simplify your management. With 10Gb Ethernet, you can also reduce your energy consumption. Consider higher capacity drives: You should consider using higher-capacity drives because it can significantly alter the storage power equation. Typical SATA disk drives consume about 50% less power per TB than equivalent-capacity FC drives. They also offer the highest available storage density per drive, further helping minimize power consumption. Keep in mind that there are many applications that still want the fast small drive, but energy criterion ought to be considered when you size up your drives. Table 6 shows the power consumption for various types of drives from Seagate: Table 6 Power Consumption by Different Disk Drives Drive Type Capacity GByte Form Facto inch Rotational Speed krpm Power Idle Watts Power Running Watts GB per Watt FC FC SAS SAS SATA

14 Use a Tiered Storage Strategy: Another strategy to consider is tiered storage. You should consider using tiered storage if the demands of storage system for your applications are different in terms of price, performance, capacity as well as functionality. For example, part of the storage system can be FC based while another part is iscsi based. You can allocate storage to your application to the correct tier on demand, and move the data between tiers. VMware ESX can address both FC and iscsi storage regardless of the drive type. Very soon, VMware storage VMotion will enable you migrate the virtual machine disk file from one storage array to another. If you have FC storage deployed, and you are looking for storage expansion in a VMware environment, this is a perfect time to look into tiered storage using IP SAN. Deploy global spare disk drive technology. Spare drives are allocated to protect against disk drive failure. However, spare drives consume energy. Therefore, to avoid having to allocate spare drives for every shelf, you should select technology that can scale and offer truly global spares. LUN best practice: Plan LUN layout based on your application workload just as you would do with physical servers. Separate heavy workloads onto separate LUNs as needed, and start with one VMFS per LUN. If you want the complete isolation, dedicate one VMFS with that VM. The number of spindles per LUN will certainly determines the number of VMs per VMFS. Networking best practice: It is always a good practice to separate iscsi traffic from general LAN traffic and use a dedicated Gigabit Ethernet based LAN for iscsi traffic. Redundant NICs are recommended for increasing bandwidth and providing high availability. By enabling flow control, you can increase overall performance and smooth IO response time. With Virtual Infrastructure 3.5 release or later, you can enable jumbo frame to reduce your server CPU utilization. Conclusions Server and Storage consolidation and virtualization go hand-in-hand. Of equal importance are networking costs and network virtualization. Whether you are a small business, or a large enterprise, it is time to take a look at how IP SAN and VMware can help you to easy your management, implementation and on-going operational costs Zanker Road, MS 200, San Jose, CA T: F: , Intransa, Inc. Intransa, the Intransa logo, StorStac, StorStac Performance, StorAR, StorCluster, DynaStac, StorOS, StorManager GUIand CLI are trademarks and business names of Intransa, Inc. All rights reserved.