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Storage expert Greg Schulz answers a reader's question: "How does SCSI in RAID compare to SATA in RAID?"

Back in 2005 someone asked the question: "Are SATA disks better than SCSI disks? Which have better performance?" Now that it is 3 years later and motherboards support RAID 0, RAID 1 and RAID 5, how does SATA in RAID compare to SCSI in RAID? Do you have any performance numbers?
In general, over the past several years there have been many improvements to SATA and RAID including RAID on a Chip (ROC) embedded on server motherboards as well as adapters. Some of the improvements beyond performance, lower cost and reduced power consumption include RAID 6 or acceleration of RAID 6, more cache memory that is battery backed up on some adapter cards and support for SAS and SATA intermix when using a SAS chipset vs. SATA chipset on a controller. If you are looking for optimum performance the SAS disk drives will perform better than the SATA disk drives generally speaking.

For performance numbers, check out the motherboard vendors or adapter vendors websites for the different alternatives. Keep in mind however that from a performance standpoint you may be comparing apples to oranges with SATA vs. Parallel SCSI as well as different adapters or ROCs may be tuned for different applications. For example, some ROCs or adapters are tuned for high throughput reads or writes while others may be tuned for lots of small I/O operations. If you are not sure where to look, check out the websites of Intel Corp., AMD Inc., LSI Corp., Atto Technology Inc. and Applied Micro Circuits Corp., among others.

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