SATA Hard Drives - Speed Jumper

[Ken C]

This is probably old news but I just found out yesterday. Some Seagate, Maxtor, and maybe other hard drive manufacturers, drives may have a speed jumper installed that limits the drive to 150 mb/s.

http://www.seagate.com/ww/v/index.js...00dd04090aRCRD

Just something to be aware of. I'm going to check out the Sage server, it's all Seagate SATA drives.

[paulbeers]

They have to do this, as older SATA150 devices can't handle SATA300 devices and so this will allow them to play nice. Truth of the matter is that no hard drive (with the exception of SSD), can actually saturate an SATA150 for more than a fraction of a second (only when pulling data directly from the cache and when your cache memory is only about 32MB, we are talking about a tenth of a second).

[stanger89]

Originally Posted by Ken C

This is probably old news but I just found out yesterday. Some Seagate, Maxtor, and maybe other hard drive manufacturers, drives may have a speed jumper installed that limits the drive to 150 mb/s.

Physics limits the drives to less than 100MB/sec anyway

Seriously though, even Seagate's new 2TB SATA 6Gb/s (SATA III IIRC) top out at about 140MB/sec, and even then only at the outer edge of the drive and performance drops precipitously toward the inner edge. So even the fastest drives (sequential transfers) out today are only beginning to approach the boundary.

And of course things are much worse in reality as sequential transfers are really not very common, something more pseudo-random is more likely. For DVR applications you're going to be lucky to get a fraction of that performance since the drive will constantly be seeking to new locations since there are probably multiple read/write operations going on simultaneously.

FWIW, this is the reason I'm looking at two WD Caviar Black (WD1001FALS) to replace my very, very aging Seagate recording drives. According to Storagereview's performance database, it's basically the fastest, reasonably large drive out there short of the Raptors (which are 10k RPM) if you have a lot IO operations going on (as you do if you've got a few tuners and extenders running). There are some faster drives, like the 1TB Hitachi and the Seagate mentioned above, but it does better in multi-user environments, see below, look at the Multi-user comparison:

http://www.storagereview.com/php/ben...3=294&devCnt=4