Re: Spurious HD convictions

[Robin Hill <robin@robinhill.me.uk>]

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On Tue Dec 15, 2009 at 11:41:03PM -0600, Leslie Rhorer wrote:

> 	It seems to have done so, yes.  I've looked around the web trying to
> find some additional info, but I've come up empty handed.  Perhaps someone
> here can answer at least one of my questions?  I know that putting a value
> of 32 into /sys/block/<driveID>/device/queue_depth fully enables NCQ, and
> putting a value of 1 there disables NCQ.  What do all the numbers in between
> do?
> 
I believe the value sets the allowed queue length.  A value of 1 thus
effectively disables queueing.  Most ATA drives have a maximum queue
depth of 32 so this is usually set for fully enabling it (though I
believe it's recommended only to use 31 - this seems to be the default).
If you set it to 32 and the drive has a shorter maximum queue, the
kernel will use the drive's maximum instead.

Setting any value is permitted, there's just generally little point in
doing so.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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