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by Quentin Beck 05/04/2007, 3:50pm PDT |
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McMoo wrote:
Solutions: New server (Opteron based, Tyan board) with SCSI RAID or SATA RAID (is SATA reliable enough? Motherhead, help!)
While proofing a point in google I came across this . Which pretty much says what I had to say better and in fewer words.
Tom Treadway wrote:
Question to the Storage Advisors, from Eric: For network storage which is better: SATA 150 or SCSI ultra360? Balance size cost and speed. We need a terabyte for live data running and storage.
Eric, there are several ways to look at this. BTW, most of what I say about SCSI also applies to SAS - the serial form of parallel SCSI.
Capacity: SATA drives are up to 1TB, while SCSI drives are still around 300GB.
Price: SATA is around 50 cents per GB, while SCSI can be as high as $2 per GB.
Reliability: SATA bit error rates are 10x that of SCSI. This is critical because errors during a RAID rebuild can cause loss of data. So with SCSI you might be able to get away with using RAID-5, but with SATA you should seriously consider RAID-6. Also, the MTBF of SCSI is reported to be 2-4X that of SATA, but thatÕs been called into question lately in the Google and CMU whitepapers.
Cabling: SATA is point-to-point, while SCSI is a shared, parallel bus. With SCSI, a cable or drive problem can bring down all of the drives. Note that this is not an issue with SAS - itÕs point-to-point like SATA.
Performance: ItÕs hard to generalize, but SCSI (and SAS) are typically higher performance than SATA. This is true of both seek times, rotational rates, and media transfer rates.
To summarize, SATA GB/$ is a LOT better than SCSI or SAS, but performance and reliability is lower. I definitely recommend that you go with a controller that supports both SAS and SATA so that you keep your options open. At this point, there is really no reason to be looking at parallel SCSI. Also, look at your access pattern and pick the right RAID level. There are plenty of posts in on this site to help you with that.
If you have any more questions, feel free to post them here. Good luck.
TT
To that I will add this. That entire article is an excellent read. Regarding your question it concludes:
AnandTech wrote:
In a nutshell, SAS, FC and SCSI drives are still the only choice for OLTP database applications, but the cheaper "Nearline", "Enterprise" and "RE" disks are probably going to chase the SCSI based drives away in the e-mail, archive, file, FTP and backup servers.
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