Traditional Storage arrays use combination of SAS/SATA disks to store data. However, if you look at the performance of these disks, its really very poor, Let's compare
SAS (Serial Attached SCSI) ~200 IOPS
SATA (Serial ATA) ~100-150 IOPS
Typically, you get above IOPS for block size of 4-8k.
But wait, storage array performance is much higher than raw SAS/SATA IOPS. How do they achieve high performance ?. The answer is Cache. The storage array use combination of Non Volatile RAM and flash disks to buffer data so I/O completed quickly with minimal latency. This architecture works fine with magnetic disks but will start to create problem when we transition to flash/Solid State disks as primary storage. Why ?. The flash/SSD Read/Write latency is so low it does not make sense to cache data any more. It will be interesting to see how storage vendors solve this bottleneck.
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