SSD versus Enterprise SAS and SATA disksby Johan De Gelas on March 20, 2009 2:00 AM EST
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- IT Computing
I/O Meter Performance (Cont'd)
Next, we test with sequential read and writes. Some storage processors (For example Netapp) write sequentially even if the original writes are random, so it is interesting to see how the disks cope with a mixed read/write scenario.
Where four SAS disks could read almost as fast as eight SATA disks, once we mix read and writes the SAS disks are slightly slower than the SATA disks. That is not very surprising: both the SAS disks and SATA disks use four platters. That means that the WD 1TB disk has a much higher data density, which negates the higher RPM of the SAS drive. Since the accesses are still sequential, areal density wins out.
As we have stated before, the SSD are especially attractive for mail and OLTP database servers. The real test consists mostly of random writes and reads. Typically, there are about twice as many reads as writes, so we used a 66% random read and 33% random write scenario to mimic OLTP database performance.