Comparative performance analysis of server disk subsystems using SSD. Part I

In the test lab DEPO Computers have already conducted tests of disk subsystems for home use. The results were described in the article “Comparative analysis of performance of PCI-E SSD, SSD and HDD drives” . The solutions described in that article are suitable for personal systems and cannot be used in servers and data storage systems, since they do not meet the requirements for reliability and fault tolerance.

Therefore, we tested several disk subsystem configurations suitable for use in servers. In our case - models of the DEPO Storm 3300 series.


Testing was conducted on the following configurations:
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• 4 x 300GB SAS2 10K + RAID10 on a PCI-E 2.0 discrete controller (Reference 4 x 300GB RAID10)
• PCI-E SSD 120GB MLC (Low Cost PCI-E SSD 120GB)
• 2 x SSD 120GB MLC + RAID0 on a PCI-E 2.0 discrete controller with SSD-optimized firmware (Budget 2 x SSD 120GB RAID0)
• 4 x 300GB SAS2 10K + RAID10 on a PCI-E 2.0 discrete controller + MLC 120GB SSD for read / write caching (Hybrid 4 x 300GB RAID10 + SSD caching)

Comparison method

In all cases, the same server configuration was used with Microsoft Windows 2008 R2 Enterprise. Performance testing was carried out by synthetic test Iometer . In comparison, performance indicators were used for random reading / writing of blocks of 4K each. The cost of one I / O operation per second and the cost of one gigabyte of usable capacity of the disk subsystem (including the controller) were also estimated.

Symbols on the graphs:

IOPS - the number of I / O operations per second
$ / IOPS - the relative cost of $ one I / O operation per second
$ / GB - the relative cost of $ one gigabyte of usable capacity

Random reading

The graph shows that when using SSD in any form, IOPS increases dramatically, which is quite natural. But beyond that, the cost of a single I / O operation per second is reduced, and it remains low regardless of the type of access to the SSD. In the case of the cost per gigabyte of usable capacity, we see a clear advantage of SSD caching - not only does this system show the maximum IOPS, but also the cost per gigabyte was just above the level of a regular disk array. It also reflects on the graph that the use of a discrete RAID controller only to implement a stripe of two SSDs is not a very budget option.

Random entry

For random write operations, the most productive option was RAID0 of two SSDs, but it also turned out to be the most expensive. In addition, it is necessary to take into account that the cost of the solution will have to be doubled to ensure fault tolerance with the transition to RAID10. A hybrid array with SSD caching showed the best result for all indicators.

Sequential reading

During streaming read operations, as we see, the usual disk array wins in all respects, the results of the recording do not differ much, so we do not give them.

findings

Of course, the data may differ depending on the size of the blocks or disks in the array. It should also be noted that in real applications in some cases absolute performance is required, rather than relative cost. But, in any case, the use of SSD for caching can significantly improve the performance of I / O operations per second for server disk subsystems.

Testing was carried out in the laboratory DEPO Computers . Trademarks and equipment manufacturers were not indicated, since The review is not advertising.

We will be grateful for all constructive feedback and recommendations.

If you have an interest in testing the performance of disk subsystems on real-world tasks and if you are ready to provide data and software for testing, we invite you to the demo center DEPO Computers.

senko ,
Lead Product Manager DEPO Computers