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SCSI Vs. SATA

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March 20, 2006 3:53:38 AM

This is fairly straight forward.
In server environments what is the most "reliable" and fastest HDD platform?

Could anyone give me the pros and cons of both?

Cheers

More about : scsi sata

March 20, 2006 6:17:16 AM

:idea: Serial Attached SCSI (SAS) combines the benefits of both SCSI and SATA into one solution. - I suggest you google that.

SATA has dedicated 'interface bandwidth' per device, so it scales far better to 6+ HDDs.

SCSI shares 'interface bandwidth' per say 6 devices (typically).

Both support command queuing, although not all SATA HDDs do.

The HDDs for each are available in 10,000 rpm models, although some faster (by seek time) SCSI HDDs are available at 15,000 rpm. (This does not make the drives +50% faster though, and sacrifices platter diameter and data transfer rate for faster seek time only, because the platters diameter is smaller the outside edge actually spins at roughtly the same speed, however their smaller size [diameter[ and high rpm mean they seek faster, so they can perform more I/O).

SAS / SATA HDDs may be available in 15,000 rpm units now.

SATA 1.5 Gbps (130 MB/sec apx) is already outperforming many older SCSI solutions in data transfer rate as is, and is very competitive seek time wise aswell.

SCSI U160 can actually bottleneck 4 HDD arrays peak performance, as the interface is not fast enough.

Do Google "Serial Attached SCSI and/or SAS", you'll find a heap of info.

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Edited: As too long :p 
March 20, 2006 7:01:44 AM

For a server you should definitely go for SCSI. As mentioned by another user, SAS is the newest iteration of SCSI, and if you can find it for your server at a reasonable price, thats the way to go. Older parallel SCSI (160 or 320) is also ok - SAS is not faster -just simpler to install.

The mayor reason for choosing/paying for SCSI/SAS over SATA, is not speed, but reliability. A SATA/PATA drive is not made for 24/7/365 operation, and it WILL fail on you. I have had several servers with both SCSI and SATA/PATA, and while I have only once had a SCSI drive fail, SATA/PATA drives on a average fails after 3 years if used in a server.

If you can buy a SAS system you can also connect a cheaper SATA drive as "bulk" storage. The SAS drives (at least 2 in a server, much more with RAID) should contain operationsystem and important server apps and the most important data-shares. The SATA is ok for data which are large (music, video and photos) and can be offline if the drive crashes.

Regards

Bo Andersen
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March 20, 2006 9:50:29 AM

Quote:
This is fairly straight forward.
In server environments what is the most "reliable" and fastest HDD platform?

Could anyone give me the pros and cons of both?

Cheers



The answer is it depends on your server hardware.

SCSI is usually better, faster, more reliable and a lot more expensive.

What kind of server hardware do you have?

If you have servers with PCI-X 64bit/133MHz slots then a multichannel SCSI controller would be faster. A 4+ channel U320 or SAS SCSI controller would be very hard to beat (4x320MB/sec = ~1280MB/sec -- of course PCI-X 64/133 = 1064MB/sec but fear not it will still be faster).

If you have servers with PCI-Express x8 or x16 slots then a multichannel SCSI controller would still be faster.

A 3Ware 9550-SX PCI-X controller might also be a good choice -- as long as you have PCI-X 64bit/133MHz slots.

There are also similar PCI-Express controllers from Areca and others that should perform about as well.

Onboard SATA controllers while cheap and widely available are terrible compared to high end storage controllers from LSI, Adaptec, 3Ware or Areca.
March 20, 2006 7:56:55 PM

Thanks everyone for your help.
One of the contractors (that I can usually trust) was telling me that SATA is the way to go. That confused me terribly, because all of my past experience SCSI has been the most reliable, and most large vendors that supply servers still implement SCSI drives into there high end systems.

Dark; Thanks for the SAS information, I have heard of the SAS drives, only through you recommending Sun Microsystems a while back, they still seem a very attractive option.

Any more links or information you could give me would be great!

Thanks
March 20, 2006 9:17:39 PM

Quote:
Thanks everyone for your help.
One of the contractors (that I can usually trust) was telling me that SATA is the way to go. That confused me terribly, because all of my past experience SCSI has been the most reliable, and most large vendors that supply servers still implement SCSI drives into there high end systems.

Dark; Thanks for the SAS information, I have heard of the SAS drives, only through you recommending Sun Microsystems a while back, they still seem a very attractive option.

Any more links or information you could give me would be great!

Thanks



Here is a good starting point:

http://en.wikipedia.org/wiki/Serial_Attached_SCSI
!