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Cc: freebsd-current@freebsd.org
Subject: Re: Are large RAID stripe sizes useful with FreeBSD?
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On 01/04/2008, Scott Long <scottl@samsco.org> wrote:

> If you have a RAID controller in front of the disks then the effects of
>  TCQ are hidden from the OS; it might ultimately make the controller
>  complete requests faster, but the controller already looks to the OS
>  like a disk with a really deep queue.  When you're dealing directly with
>  the disks then TCQ/NCQ is required in order for batching of concurrent
>  requests to occur.

Thanks. I thought TCQ is also used between the OS and the controller
(since the RAID array is presented to the OS as opaque...).