Using FATA disks for primary storage?

[GilchristT]

I was talking to a customer today and he wants to buy a SAN but doesn't see why he should pay the premium for SCSI disks when FATA disks would do rightly. I had no figures to explain why not!

Has anyone any experience of using FATA for primary storage? I was wondering what the performance would be like compared to say a MSA1000 with 10K SCSI disks?

I've only ever used FATA for backup to disk

thanks

tommy

[Steven Clementi]

Tommy:

Tell your customer that FATA disks have a higher failure rate. See how he/she responds.


The fact is, ANY ATA drive is NOT meant to be running full Duty Cycle all of the time. The drive is simply not designed to run for that long.

SCSI vs. SATA or FIBRE vs. FATA... sure the MTBU is about the same. Read the details about the how the MTBU was determined.

I do not know for a fact, but was told that SCSI/FIBRE drives were measured at @80% Duty Cycle while SATA/FATA drives were measured at @30% Duty Cycle.


Steven

[pswma2]

Tommy,

FATA disks have only one controller internally, FC(SCSI) disks have two. The visible difference is the responce time under load. We have EVA-4000 with 56 FATA disks in it and are using the system for backup only. If you just try a simple "ls" command on the directory which is on this storage you get the responce 3-4 seconds later.
These are really not the disks you can recommend for a database or I/O active application.

[GilchristT]

Thanks folks

Some useful thoughts and figures there

tommy

[The Spartan]

1. FATA HDDs are termed nearonline.
Reason:
They cannot manage/handle i/os as effectively as SCSI.
MTBF is much less in FATA than SCSI.
They are less expensive as they are less robust.
They are NOT meant for online transaction, as DATA integrity is threatened if the same is done.

Regards.

[Alzhy]

It depends on his usage.

If the load on the FATA array/diskgroup will just be for simple file serving or light database duty - I do not see why not?

The high failure rates can be compensated by utilizing host based mirrors and even dual redundancy and hot spares...

As far as performance, I think the gap is closing... In fact on our EVA5K's with FATA500 drives -- we hardly noticed any difference (performance) with the FC300 drives...

[Francois_20 · Accepted solution]

The same reason why you don't buy a ferrari and put a VW motor in it :-)

I can only echo what the guys are saying. We also only use FATA for backups. Believe me when I say, it is not used for speed or IO.

The only real reason one even use backup to disk, is to add an additional "recovery" layer. (Especially when using FATA)

We get much better speeds backing up to an 8 x 146GB MSA (Raid5) than to (24 x 250GB) FATA (Raid5). Which clearly highlights the difference in SCSI vs FATA.

Cheers.