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

[Justin Piszcz]

On Mon, 24 Nov 2008, Eric Sandeen wrote:

> Stian Jordet wrote:
>> ma., 24.11.2008 kl. 04.50 -0500, skrev Justin Piszcz:
>>> While there still may be something else wrong, the first problem I see is
>>> your sunit and swidth are set to 0.
>>>
>>> Please read, a good article on what they are and how to set them:
>>> http://www.socalsysadmin.com/
>>
>> Oh, this was new to me. But the setting didn't change anything. I can
>> copy one large file between the xfs and ext3 disk (both ways), and I get
>> speeds between 160 and 200 MB/s. But unpacking the kernel source takes
>> between 5 and 10 minutes on the xfs disk, and a mere 15 seconds on the
>> ext3... (and it also used to take between 5 and 10 minutes when I had
>> xfs on the raid0, so it doesn't seem to be hardware related...)
>>
>> If anyone has anything more I can try before I do the lengthy process of
>> backup 1TB, reformat and restore...
>
> I don't know if the storage you're on passes barriers or not, but xfs
> has barriers on by default, while ext3 does not.  ext3 will still likely
> win the "untar a kernel" race, but for a fairer test, make the barrier
> settings consistent between the two.
>
> -Eric
>

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