Re: Are large RAID stripe sizes useful with FreeBSD?

On 31/03/2008, Scott Long <scottl@xxxxxxxxxx> wrote:

For writes, the performance penalty of smaller I/O's (assuming no RAID-5
effects) is minimal; most caching controllers and drives will batch the
concurrent requests together, so the only loss is in the slight overhead
of the extra transaction setup and completion. For reads, the penalty
can be greater because the controller/disk will try to execute the first
request immediately and not wait for the second part to be requested,
leading to the potential for extra rotational and head movement delays.
Many caching RAID controllers offer a read-ahead feature to counteract
this. However, while my testing has shown little measurable benefit to
this, YMMV.

Thank you, this is the kind of explanation I hoping for. One more
thing: is TCQ (e.g. the SCSI variant) orthogonal to this?
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