POWERVAULT MD3000 AND MD3000i ARRAY TUNING BEST PRACTICES dell.com/PowerVault...
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices DISCLAIMER THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND.
Tuning the system to maximize performance of multiple applications that may share a single storage array can seem even more formidable. To reduce the complexity of tuning, Dell™ storage systems feature performance monitoring and flexible tuning controls that can be accessed through the Modular Disk Storage Manager (MDSM).
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices The answers include: • “It depends…” There are no absolute answers. Each environment is unique and the correct settings depend on the unique goals, configuration, and demands for the specific environment.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices • Profile of mean I/O direction; this is usually the ratio of Reads to Writes 4 Configuring the MD3000/MD3000i There are two ways to configure the MD3000 and MD3000i storage systems.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Physical disk cost is not the only factor that influences the decision on which RAID level is most appropriate for a given application. The performance of a chosen RAID level is heavily interdependent on characteristics of the I/O pattern as transmitted to the storage array from the host(s).
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices 4.1.1 Selecting a RAID Level - High Write Mix Scenario In random I/O applications with a >10% mix of write operations and a low degree of burstiness, RAID 1/10 provides the best overall performance for redundant disk groups.
Dell™ does not recommend using more than four virtual disks or repositories per disk group for peak performance. Additionally, where performance is critical, isolate virtual disks to separate disk groups as possible. When multiple high- December 2008 – Revision A01 ...
4.4 Virtual Disk Ownership The Dell™ MDSM can be used to automatically build and view virtual disks. It uses optimal settings to stripe the disk group. Virtual disks are assigned to alternating RAID controllers when they are created.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices first 128KiB of an I/O is written to the first drive, the next 128KiB to the next drive, and so on with a total stripe size of 512KiB. For a RAID 1, 2 + 2 virtual disk group, 128KiB would be written to each of the two drives (and same for the mirrored drives).
Additionally, the global cache block size for read and write cache can be adjusted through the CLI. Please refer to the Dell™ PowerVault™ Modular Disk Storage Manager CLI Guide on the Dell™ technical support site (http://support.dell.com/manuals) for a complete list of supported commands including the following cache specific commands.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices 4.6.3 Setting the Storage Array Cache Block Size Configured through the CLI – This command is available at the storage array level and effects all virtual disks and disk-groups. Cache Block Size – Cache Block Size refers to the way cache memory is segmented during allocation and affects all virtual disks in an array.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices 4.7 Tuning Using Array Performance Data 4.7.1 Collecting Performance Statistics The stateCaptureData.txt and performanceStatistics.csv files, which are available through the MDSM, Support tab as part of a Technical Support Bundle, provide valuable statistical data in an easy-to-read format.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices to how tightly the variance of sequential or random data access is contained within the volume. This can be purely random across an entire virtual disk, or random within some bounds, such as a large file stored within a virtual disk compared to large non-contiguous bursts of sequential data access randomly distributed within some bounds.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices In the first generation of firmware (see Figure 5), this can be determined from the ‘Avg. Blocks’ row which represents the average I/O block size encountered. In Generation One, the ‘Large IO’ field denotes a 4096 block or 2MiB size with zero registered Large Reads or Writes during the sample period.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices In addition, the stateCaptureData.txt file provides a more granular method for determining the distribution of I/O within stripes and segments. In Figure 7 and Figure 8, item 1 is the number of full stripes read and written, and item 2 indicates the number of full clusters or segments read or written.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices RMW, or Read-Modify-Write, is the second-best write algorithm available for RAID 5 and 6. A RMW occurs when a quantity of bits, smaller or equal to an individual segment are modified. This constitutes a two-read operation in RAID 5 and a three-read operation in RAID 6, with one of the segments being modified, and the parity drive(s) are read in.
In Microsoft Windows, the scripting utility is named smcli.exe and is located by default in the c:\program files\Dell\MD Storage Manage\client directory. The complete reference guide Command Line Interface Guide for the MD3000/3000i is located on Dell’s support website at http://support.dell.com/manuals. The following are examples of CLI commands.
Set up and use Global Media Scan for low access logical drives, for example, file storage drives. Please note that Dell™ does not recommend disabling media scan or lowering the media scan interval below 15 days. If Media-Scan is disabled, the risk of non-predicted failures can increase.
HBAs sharing a single bus can throttle the bandwidth. Additionally, some server hardware has slower-speed PCI- E ports (4x) as well as high-speed ports (8x). The Dell SAS5e HBAs are PCI-E 8x devices and should be installed in 8x slots for maximum performance. Where...
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Figure 11: MD3000i Advanced IPv4 Settings: VLAN, QOS, Jumbo Frames Support 5.1.3 Sharing Bandwidth with Multiple SAS HBAs Each SAS wide port includes four full duplex serial links within a single connector.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices used at certain times, providing a point-to-point raw wire speed of up to 12Gb/s. Please note that this raw speed does not take into account the transmission overhead or device spenditures on either side of the SAS wide link and is purely a cached I/O operation.
Microsoft provides the diskpar.exe utility as part of the Microsoft Windows 2000 Resource Kit, which was renamed to diskpart.exe in Microsoft Windows 2003 and later. Microsoft has a KB article 929491 covering this, and Dell™ always recommends checking for proper partition alignment to the stripe size of assigned virtual disks.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Appendix A: Obtaining Additional Performance Tools Table 3 shows a number of widely available tools, benchmarks, and utilities. Some of these tools are produced by non-profit organizations and are free. Table 3: Performance Tools...
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Appendix B: System Troubleshooting For information about troubleshooting MD3000 and MD3000i storage arrays, refer to the “Troubleshooting Problems” chapter of the Dell™ PowerVault™ Modular Disk Storage Manager User’s Guide. Go to: MD3000: http://support.dell.com/support/edocs/systems/md3000/en/index.htm...
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Appendix D: Glossary of Terms Term Definition A data traffic property defined as the ratio of the peak Burstiness I/O rate to the average I/O rate; in this case, the mean duty cycle exhibited by I/O transmitted or received from a storage array.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Term Definition directly on the drive in lieu of using an SATA interposer. Redundant Array of Inexpensive Disks RAID RAID Level 0; RAID 0 is a striped set with no redundant RAID 0 information.
Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices Term Definition by t10.org A segment is the data written to one drive in a virtual Segment disk group stripe before writing data to the next drive in the virtual disk group stripe.