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Sequential Read & Write Patterns

IOMeter is sending a stream of read and write requests with a request queue depth of 4. The size of the requested data block is changed each minute, so that we could see the dependence of the array’s sequential read/write speed on the size of the data block. This test is indicative of the highest speed the array can achieve.

You can click the following links for tabled results:

The HDDs split up into three groups when working in RAID0 arrays. Samsung’s T133S series drives and the WD4000ABYS are the fastest here while the WD4000YS is the loser (although the latter achieves its maximum speed sooner than the other drives). The third group show medium speeds.

There are no changes in the standings when we switch from RAID0 to RAID10.

There are certain changes in RAID5. The Samsung HD400LJ achieves its maximum speed later than the other T133S series drive but its maximum speed is higher than the latter’s.

The overall picture changes considerably when we are writing to the RAID0 arrays. We have the same leading trio consisting of the WD4000ABYS and Samsung’s T133S drives, but the HD401LJ has firmware flaws that lead to a performance hit on very large data blocks. The Samsung T166S is now slower than most of the drives.

The HD401LJ has no problems with large data blocks in a RAID10 array but its speed is just slower than that of the model with a smaller buffer.

Every HDD has speed fluctuations on large data blocks when working in a RAID5. This array type is sensitive to the data block size and each HDD model has its own way of treating different data chunks.

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