Are large RAID stripe sizes useful with FreeBSD?

Ivan Voras ivoras at
Mon Mar 31 15:18:32 PDT 2008

On 01/04/2008, Scott Long <scottl at> 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...).

More information about the freebsd-current mailing list