What is a SAS hard disk drive?
I’ve been reading up on different types of high-end workstations and am a bit puzzled about an expensive drive alternative to the usual SATA: an “SAS” hard disk. What’s SAS and why would I want to even consider it?
Great question. I had no idea, so instead I asked Matt Lawson of Microsel to illuminate us on what SAS drives are why they might be a great choice for your new system. Here’s what he shared:
SAS stands for Serial Attached SCSI. Basically, a SAS drive utilizes the same form factor as a SATA drive but has several high performance advantages. First of all, there’s the platter speed. While typical SATA drives operate at 7200RPM, a SAS drive operates at 10K or 15K. Although the platter speed is double that of SATA, the MTBF (Mean Time Before Failure) remains at the industry standard of 1.2 million hours.
SAS drives are typically utilized in server and high-end workstation environments where speed and I/O frequency reign supreme. Now, that being said, there are oh SOOOO many factors in building a screaming fast, but rock-solid, workstation or server.
Where speed is concerned, you need to be looking at the right drives first and foremost. Nowadays, I tend to spec in a couple of SSD’s (Solid State Drive) in a RAID 0 (Redundant Array of Inexpensive Disks) for the boot and applications drive, then for scratch disks/additional storage, I like to do 3-5 or more SAS drives in a RAID 5 (best mix of redundancy and speed, with the addition of parity).
That being said, there are larger considerations, such as the RAID stripe size (or stripe width). The stripe size determines what size blocks of data will be sent to each drive in the array. It’s imperative (where speed is concerned)
that the engineer do his job in determining what the server will be used for. If the application the server is built for houses small files, or is a file server for smaller files, you want to choose a small stripe size, say 256KB or so. Now, for people doing database work, photo/video/audio editing, rendering or production, they need as big a stripe as the controller allows for. For those types of applications, as stripe size of 2MB or higher (if allowed by the controller) is a must.
Last but not least, where stability is concerned, the drives must be properly paired (this is something that 90% of the builders in the world are oblivious to which, in turn, can make MY job very difficult as it tends to give the entire white-box market a black eye). If drives in a RAID array are not properly matched by Firmware version, the odds are that at least one of the drives will fall out of the array within the first year. Depending on the type of array chosen, this could simply mean the company has to foot the bill for higher hardware costs, or be as bad as catastrophic data loss.
There are a few key factors I like to hit on when I’m building a client a new workstation or server for the first time. I match Firmware on the drives, step codes on the processors (if they are doing a dual processor system) and match batch codes on the RAM. Those three factors will determine, from a stability stand-point, whether or not the server will stand the test of time.
Contributor Matt Lawson is a native Coloradoan whom has been engineering custom electronics systems for the past decade and is a certified Systems Engineer for Microsel of ColoradoSource: www.askdavetaylor.com