Has anyone got a link on the advantages between these two speeds of SCSI dirves and how much difference it actually makes? Who here uses 15k drives?

Take a look at http://www.storagereview.com

Its a great site for comparations and reviews with a lot of usefull info... also informative forums... there you should find the answer you are looking for...

Also, 15K drives have much faster seek times giving your better performance, for example, the best rated 10K (Maxtor ATLAS 10K III) have 4.5 average seek time, compared to the best 15K (Seagate Cheetah 15X-36) with a 3.6 average seek time, the Maxtor its slow...

but this difference in time worth to pay the difference in price?, I really don't know if you will notice it... maybe there is more experienced people in this forum that can help us with this...

If your application depends heavily on I/O - a very high load mail server, news server etc, then you need to pick 15k RPM drive for top notch speed and low seek times.

Thanks. When is the difference going to kick in? is it only on a heavily used server? or is it going to make much of a difference straight away? This is a database server I am thinking about so it would have large I/O.

Originally posted by padders
Thanks. When is the difference going to kick in? is it only on a heavily used server? or is it going to make much of a difference straight away? This is a database server I am thinking about so it would have large I/O.

The transfer speeds between the two drives should be the same, just the seek times different, meaning that if you're copying large files, no difference, but when dealing with thousands/millions of tiny files, the second 15k one will move 25% faster (by those numbers, 4.5 3.6) give or take :).

it would be for mySQL so not really lots of small files ...

Originally posted by porcupine


The transfer speeds between the two drives should be the same, ....


Not necessarily the same. With the 15krpm drives, 50% more surface area moves under the read head per unit of time. So, theoretically at least, the 15krpm drives should have a higher transfer rate.

Originally posted by Mike the newbie



Not necessarily the same. With the 15krpm drives, 50% more surface area moves under the read head per unit of time. So, theoretically at least, the 15krpm drives should have a higher transfer rate.

You would think so, but think of 5400 and 7200 drives, theres a definite speed difference in platter rotation speed there, but the transfer rates remain the same.

Originally posted by Mike the newbie
With the 15krpm drives, 50% more surface area moves under the read head per unit of time. So, theoretically at least, the 15krpm drives should have a higher transfer rate.

Yes, except that in order to run drives at 15kRPM, the platters are typically made smaller, which reduces the transfer rate again.

Basically, high RPM drives are useful for anything which fsync()s often. That means mail servers (if you're handling a million emails/day), and database servers, but not http servers (unless you're very short on memory).

We have servers with both and you can see a small difference under light loads, but it really starts to shine under moderate/heavy loads. As others have said, the work really well for Mail & Database servers.

They are much faster, but I really don't have any numbers to back that up. Just my observations :)

Originally posted by porcupine


You would think so, but think of 5400 and 7200 drives, theres a definite speed difference in platter rotation speed there, but the transfer rates remain the same.

The Cheetah X15 15krpm SCSI drive has a max internal transfer rate of 706 Mbits/sec. The Western Digital 7200rpm Caviar has a maximum internal transfer rate of 602 MBits/sec. So there is an improvement in throughput with the 15krpm drives.

On the other hand, data densities are lower for the 15krpm drives, so that negates some of the rpm improvements.

Depending upon how you intend to use the drives, either data transfer rates or seek times may be more important. It is tough for a 7200rpm drive to beat the rotational latency of a 15krpm drive. This gives the high rpm drives an edge in multi-user environments, or when doing lots of small reads or writes.

Quite frankly though, with the 8MB buffers in the new WD Caviar drives, the performance edge of SCSI is dwindling. The tagged and queued i/o capability of SCSI was a big difference that is becoming moot.

Definatly well said. I say if you're really concerned about the speed, setup a RAID configuration on multiple 7200RPM ide drives with lotsa cache, and a good RAID card, if you can find RAID 5 for IDE (i've never used one, dont even know if they make raid 5 for IDE to be honest) and 3+ 7200 drives, you'd probably be paying near the same for the SCSI 15k, and you would get redundancy, speed, and space with that type of configuration for the same price.

Of course, im a tightwad and thats just my two cents :)... can i have those two cents back? :D

If you are only looking for read performance, then RAID 5 is fine. However, if you also need high-speed write performance, investigate RAID 0/1.

i've never used one, dont even know if they make raid 5 for IDE to be honest3Ware; http://www.3ware.com/products/escalade.asp