SATA does not do Read's Writes's at the same time well (ie Migration or
backup Stgpool with Backup client session at the same time...   It can be
done, but careful concideration is taken when the SATA Disk Frame is
carved up... (ie striped accross Drawers, small raid groups etc)
The easiest is a Tier 2 FC frame ...

Charles Hart





"Allen S. Rout" <asr AT UFL DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
07/12/2007 09:19 AM
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Re: [ADSM-L] SATA disk?






>> On Thu, 12 Jul 2007 07:32:27 -0500, Andy Huebner
<Andy.Huebner AT ALCONLABS DOT COM> said:

> To me it is not the incoming, but the outgoing that is the greatest
> concern.  If the next pool is physical tape, be sure you have enough
> speed to keep up with your tape drives.  If the disks cannot keep up
> with the physical tape drives then performance will not be acceptable.
> Since many VTLs use ATA disks we know it can be done.


This is a really good point.  Keeping the number of read streams under
control will make a huge difference in your performance.

When I drain a SATA pool with a single thread, I can drive one of my
3592s at 80-90 MB/s.  When I put three of them on the job, aggregate
throughput drops to ~30 MB/s (yes, each drive getting ~10MB/s).

- Allen S. Rout



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