Are large RAID stripe sizes useful with FreeBSD?

Ivan Voras ivoras at
Mon Mar 31 14:34:09 PDT 2008

On 31/03/2008, Scott Long <scottl at> 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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