Enterprise Class SATA Drives versus SCSI Drives

[Alzhy]

Am specing storage for Proliant machines and am considering going for SATA drives. But are the drives offered by HP considered "Enterprise CLass"? By enterprise class I mean -- MTBF's approaching at least 1 million hours.

Western Digital Raptor 10K RPM SATA (150 or 300?) drives are being positioned as Enterprise class and have rated MTBFs of over 1 million hours. Are these the same drives that HP uses?

I know, SCSI is still better but the price difference is just so much.

[Uwe Zessin]

As far as I can tell, HP is using Maxtor. Whether SATA drives are 'enterprise class' or not, that's debatable and depends on your definition of 'enterprise class' ;-)

I didn't get a feeling that HP thinks they are. At least they have told us on trainings not to position them wrongly and I have been in customer sessions where they told the same. (Don't expect high performance from them, don't exercise them too much, expect a higher failure rate).

There are some specific cases where a SATA drive can outperform a SCSI drive, but they have to do with the drive's geometry when looking at spiral transfer rates. Not many of our customers have that need.

I am surprised by that high MTBF! I've been told that SATA drive vendors don't want to give more than one year of warranty for their iron. The drive vendors use the MTBF to calculate the required number of spares, so a miscalculation can be a bit, ahem, 'unpleasant'.

SCSI isn't inherently 'better'. HP positions SATA for so-called 'reference data'. That is data which is stored on disk for easy access, but which is not accessed frequently. In that case you can live with a disk drive that has a lower duty cycle.

I haven't looked at the specs for the WD Raptor - it might be that this is a hybrid like the FATA disk drives for the EVA. I've talked to one of the drive qualification engineers of the EVA team and he said that their FATAs are more robust like a cheap(my word) SATA disk drive.

[Duncan Edmonstone]

I guess the question is, what duty cycle are the MTBF figures based on? Sometimes MTBF figures for SATA disks are based on a duty cycle (i.e. heads spinning) of around 30%, vs. a duty cycle of 100% for SCSI/FC disks.

What is the storage to be used for? If its in any way critical I'm sorry but I'd still go with SCSI/FC any day.

HTH

Duncan

[Uwe Zessin]

Yes, that's right. I can't quote any exact numbers, but I have once seen a table and the MTBF was reduced rather quick by a higher duty cycle.

[Alzhy]

I have no idea what duty cycles WD based thier MTBF ratings on but the drives are warranted for 5 years.. basically at par with their FC/SCSI cousins.

I have the initial 36Giggers runing on a gaming/GP machine (x86) for about 6 months now and so far they have not died down on me and their performance is what the vendor claims.. I have not figured out yet whether they're SATA/300 compliant but I am sure my SATA controller is still at SATA/150...