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sas - SCSI vs SATA? Is SCSI "actually" better?




Well, I was talking with a guy about servers the other day. I was a bit shocked whenever I asked him if there was any significant difference between SCSI and SATA and why he always uses SCSI. (note, I'm not sure if by SCSI he meant SAS)



He told me that SCSI is always faster and that the drives are always more reliable.. I mean, this seems like a bold statement.



He told me something about how SCSI will always be faster than SATA because the OS sends the SCSI (controller?) a request to get a file and it will build the file inside of the SCSI controller, instead of searching all over the disk.. which I do not understand how that would work, so I figure it is BS.



SAS and SATA currently have equivalent data rate speeds..




Is there any true backing for his reasoning that SCSI is always faster and more reliable than SATA?


Answer



For SATA, you need to be careful about using a consumer drive if you are building a RAID array.



Some power saving features and in the case of Western Digital, some of their SATA drives have a "deep recovery" process when an error is detected. These can cause a SATA RAID member to be dropped or marked as failed if it is unresponsive beyond the timeout period.



When a SATA RAID5 volume with huge drives drops a member, it is not uncommon for the rebuild to take several hours. During this time, performance will be abysmal.



Western Digital - difference between Desktop edition and RAID (Enterprise) edition hard drives?

http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1397



http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery


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