suggestions for SATA RAID cards

[Matthew D. Fuller]

On Wed, Oct 04, 2006 at 04:11:47PM +0100 I heard the voice of
Pete French, and lo! it spake thus:
> > Blocksize in RAID 1?
> 
> Yes, it puzzled me too! I think the Compaq controllers only have 0+1
> though, so you need to give a stripe size even with only two drives
> mirrored - and if you watch the activity lights and do a sequential
> read it flips from one drive to the other.

I would guess that's nothing to do with blocks or striping per se.  A
single big file won't be laid out 'sequentially' on the disk; the
filesystem tries to avoid filling up cylinder blocks.  It puts enough
in given places that the seek costs are pretty low.  So, after reading
one bit a while, it'll seek somewhere and start another read.  The
controller could issue that read to another component of the mirror;
I'd expect a sufficiently smart RAID controller to even out across the
disks, even when there's only one process reading (not that the
controller knows anything about 'processes', but...)


-- 
Matthew Fuller     (MF4839)   |  fullermd at over-yonder.net
Systems/Network Administrator |  http://www.over-yonder.net/~fullermd/
           On the Internet, nobody can hear you scream.