just beeing curious:
does your SATA controller and disks support NCQ/TCQ and ist either of them
enabled?
Is write cache on Disks enabled?
I am only extrapolating from SCSI experiences - command queuing and disk write
cache can slow-down the raid (if both inactive)
Juraj
> -----Ursprüngliche Nachricht-----
> Von: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] Im
> Auftrag von John Monahan
> Gesendet: Dienstag, 20. Juni 2006 21:35
> An: ADSM-L AT VM.MARIST DOT EDU
> Betreff: Re: TSM diskpool on SATA
>
> > Did you do any FILE devclass work? It sounds as though
> your miserable
> > performance was head thrashing, which we'd get in multiple LV DISK
> > devclasses, and also in FILE devclasses. Darn. :)
>
> No I was using a DISK devclass, but I'm almost positive it
> wouldn't have made any difference with FILE devclasses. Some
> of the LUNs were faster than others (first ones in the RAID
> group created) and as soon as I was writing to more than one
> at a time my performance would tank even further, which
> shouldn't be any different had I used FILE devclasses. I
> would have tried file devclasses with more time for
> performance reasons, but I had spent too much time on it
> already and the 150 MB/sec writes for my diskpool was
> adequate for my needs and outpaced the capabilities of my
> single Gigabit network connection to the TSM server, so I moved on.
>
> Hundreds of LVs with FILE devclasses on fibre disks would
> probably do exactly what you are looking for and provide
> excellent performance. SATA just isn't good enough at
> multiple, simultaneous I/Os to the same set of disks yet.
>
|