Extreme slowness with xfs [WAS: Re: Slowness with new pc]

[Christoph Hellwig]

On Tue, Nov 25, 2008 at 04:56:24AM -0500, Justin Piszcz wrote:
> barriers enabled:
> 
> $ time bash -c 'tar xf linux-2.6.27.7.tar; sync'
> block 573932: ** Block of NULs **
> Total bytes read: 293857280 (281MiB, 1.9MiB/s)
> 
> real    2m40.643s
> user    0m0.194s
> sys     0m1.541s
> 
> barriers disabled:
> 
> time bash -c 'tar xf linux-2.6.27.7.tar; sync'
> block 573932: ** Block of NULs **
> Total bytes read: 293857280 (281MiB, 11MiB/s)
> 
> real    0m27.612s
> user    0m0.182s
> sys     0m1.617s

That's worse than usual, and even the no-barriers numbers are still
really bad.  What kind of disk and controller is this?  Did you
try to disable the cache with hdparm and see what that gives?