PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Information Science & Engineering SOLUTION MANUAL INTERNAL ASSESSMENT TEST 1 Subject & Code : Storage Area Networks / 15CS754 Name of faculty: Prof. Animesh Giri / Prof. Preeti Sangamesh Class: 7 th semester CSE/ISE (Common Elective) 1. Explain the core elements and key characteristics of Data Centre elements with a neat diagram (08Marks) Answer: Data Centre: It is a facility that contains storage, compute, network, and other IT resources to provide centralized data-processing capabilities. Core elements of a data center Application Database management system (DBMS) Host or Compute Network Storage These core elements work together to address data-processing requirements Key Characteristics of a Data Center Key management activities include
Monitoring Continuous process of gathering information on various elements and services running in a data center Reporting Details on resource performance, capacity, and utilization Provisioning Configuration and allocation of resources to meet the capacity, availability, performance, and security requirements 2. Discuss the functionalities of a Logical Volume Manager, with a neat diagram 08 Marks
LVMExample: Partitioning and Concatenation Hosts Logical Volume Physical Volume Partitioning Concatenation EMC Proven Professional. Copyright 2012 EMC Corporation. All Rights Reserved. Module 2: Data Center Environment 11 3. Define the two main goals of RAID; Explain the below mentioned RAID techniques with suitable diagrams. a. RAID 1+0 b. RAID 0+1 Explain why RAID 0 is not an option for data protection and high availability? (08 Marks) Answer: Performance limitation of disk drive An individual drive has a certain life expectancy o Measured in MTBF (Mean Time Between Failure) o The more the number of HDDs in a storage array, the larger the probability for disk failure. For example: o If the MTBF of a drive is 750,000 hours, and there are 100 drives in the array, then the MTBF of the array becomes 750,000 / 100, or 7,500 hours o RAID was introduced to mitigate this problem o RAID provides: o Increase capacity o Higher availability Increased performance RAID LEVELS o 0 Striped array with no fault tolerance o 1 Disk mirroring
o Nested RAID (i.e., 1 + 0, 0 + 1, etc.) o 3 Parallel access array with dedicated parity disk o 4 Striped array with independent disks and a dedicated parity disk o 5 Striped array with independent disks and distributed parity o 6 Striped array with independent disks and dual distributed parity NESTED RAID o Combines the performance benefits of RAID 0 with the redundancy benefit of RAID 1. o RAID 0+1 Mirrored Stripe o Data is striped across HDDs, then the entire stripe is mirrored. o If one drive fails, the entire stripe is faulted. o Rebuild operation requires data to be copied from each disk in the healthy stripe, causing increased load on the surviving disks. o RAID 1+0 Striped Mirror o Data is first mirrored, and then both copies are striped across multiple HDDs. o When a drive fails, data is still accessible from its mirror. o Rebuild operation only requires data to be copied from the surviving disk into the replacement disk. 4. An application has 1,000 heavy users at the peak of 2 IOPS each and 2,000 Typical users at the peak of 1 IOPS each, with read/ write ratio of 2:1. It is also estimated that the application also experiences an overhead of 20 Percent for other workloads. Calculate the IOPS requirements for RAID 1, RAID 3, RAID 5, and RAID 6. 5. Define Intelligent Storage Systems? Explain with a neat diagram the components of an Intelligent Storage Systems. (08Marks)
Answer: It is a feature-rich RAID array that provides highly optimized I/O processing capabilities. Provides large amount of cache and multiple I/O paths that enhances the performance Has an operating environment that provides Intelligent cache management Array resource management Connectivity to heterogeneous hosts Supports flash drive, virtual provisioning, and automated storage tiering Key Components of an ISS Key Components of an ISS Intelligent Storage System Host Front End Back End Physical Disks Connectivity Storage Network Cache EMC Proven Professional. Copyright 2012 EMC Corporation. All Rights Reserved. Module 4: Intelligent Storage System 5 6. Explain the Cache functionalities in Intelligent Storage System (08 Marks) Answer: Cache is semiconductor memory where data is placed temporarily to reduce the time required to service I/O requests from the host. Structure of Cache Cache consists of the data store and tag RAM. The data store holds the data while tag R. Tag RAM includes a dirty bit flag, which indicates whether the data in cache has been committed to the disk or not
Read Operation with Cache RAM to determine whether the required data is available in cache. If the requested data is found in the cache, it is called a read cache hit or read hit and data is sent directly to the host, without any disk operation If the requested data is not found in cache, it is called a cache miss and the data must be read from the disk A pre-fetch, or read-ahead, algorithm is used when read requests are sequential. In a sequential read request, a contiguous set of associated blocks is retrieved. Write Operation with Cache Write operations with cache provide performance advantages over writing directly to disks. When an I/O is written to cache and acknowledged, it is completed in far less time (from the host s perspective) than it would take to write directly to disk Write-back cache: Data is placed in cache and an acknowledgment is sent to the host immediately and committed later. Cache Implementation Cache can be implemented as either dedicated cache or global cache. With dedicated cache, separate sets of memory locations are reserved for reads and writes. In global cache, both reads and writes can use any of the available memory addresses. Cache Management Least Recently Used (LRU): An algorithm that continuously monitors data access in cache and identifies the cache pages that have not been accessed for a long time. Most Recently Used (MRU): An algorithm that is the converse of LRU. In MRU, the pages that have been accessed most recently are freed up or marked for reuse.
On the basis of the I/O access rate and pattern, high and low levels called watermarks are set in cache to manage the flushing process. Idle flushing: Occurs continuously, at a modest rate, when the cache utilization level is between the high and low watermark. High watermark flushing: Activated when cache utilization hits the high watermark. The storage system dedicates some additional resources to flushing. This type of flushing has minimal impact on host I/O processing. Forced flushing: Occurs in the event of a large I/O burst when cache reaches 100 percent of its capacity, which significantly affects the I/O response time. In forced flushing, dirty pages are forcibly flushed to disk.
Cache Data Protection Cache mirroring: Each write to cache is held in two different memory locations on two independent memory cards. Cache vaulting: Cache is exposed to the risk of uncommitted data loss due to power failure. This problem can be addressed in various ways: powering the memory with a battery until AC power is restored or using battery power to write the cache content to the disk. 7. Explain the components of Storage Area Networks (SAN)? Illustrate transmission of data in Fibre Channel Arbitrated Loop (FC-AL) configuration with a neat diagram. Answer: o Dedicated high speed network of servers and shared storage devices o Provide block level data access o Resource Consolidation o Centralized storage and management o Scalability o Theoretical limit: Appx. 15 million devices o Secure Access
Components of SAN: Node ports
FC- AL Transmission o Fibre Channel Arbitrated Loop (FC-AL) o Devices must arbitrate to gain control o Devices are connected via hubs o Supports up to 127 devices
8. Discuss the layers of Fibre Channel Protocol Stack; also explain different types of Fibre Channel Ports with a neat diagram. Answer: o FC uses channel technology o Provide high performance with low protocol overheads o FCP is SCSI-3 over FC network o Sustained transmission bandwidth over long distances o Provides speeds up to 8 Gb/s (8 GFC) o FCP has five layers: o FC-4 Upper Layer o FC-2 - Transport Layer o FC-1 Transmission Protocol o FC-0 Physical Interface *FC-3 is not yet implemented
Fibre Channel Ports
9. Explain storage provisioning methods? Compare the virtual and traditional storage provisioning methods with a neat diagram. Shown is an example comparing Virtual Provisioning (on the right) with traditional storage provisioning (on the left). The example demonstrates the benefit of better capacity utilization. With traditional provisioning, three LUNs are created and presented to one or more hosts, using traditional provisioning methods. The total usable storage capacity of the storage system is 2 TB. The size of LUN 1 is 500 GB, of which 100 GB is actual data and 400 GB is allocated unused capacity. The size of LUN 2 is 550 GB, of which 50 GB is actual data and 500 GB is allocated unused capacity. The size of LUN 3 is 800 GB, of which 200 GB is actual data and 600 GB is allocated unused capacity. In total, the storage system stores 350 GB of actual data, 1.5 TB of allocated unused capacity, and only 150 GB of available capacity for other applications. If we consider the same 2 TB storage system with Virtual Provisioning, the differences are quite dramatic. Although the system administrator creates the same size LUNs for LUNs 1, 2, and 3, there is no allocated unused capacity. In total, the storage system with Virtual Provisioning stores the same 350 GB of actual data as the other storage system, with 1.65 TB of capacity available for other applications, versus only 150 GB in the traditional storage system.
10. Discuss the feature of Midrange Storage Systems and High-end Storage Systems with a neat diagram. (08Marks) Answer: Midrange Storage Systems Referred as active-passive arrays, and generally aimed at small and medium-sized enterprise applications Performs I/Os to LUNs only through active paths These arrays typically have two controllers, each with cache, RAID controllers, and disks drive interfaces Less front-end ports, storage capacity, and cache as compared to high-end arrays Support local and remote data replication High-end Storage Systems Referred as active-active arrays, and generally aimed at large enterprise applications. Performs I/Os to LUNs through all the available paths These arrays provide the following capabilities: Large storage capacity and cache Fault tolerant architecture Connectivity to mainframe and open systems Multiple front-end ports and interface protocols Ability to handle large amount of concurrent I/Os Support local and remote data replication