Re: Strange delays on NFS server

[Ian Thurlbeck <ian@stams.strath.ac.uk>]

Greg Banks wrote:
> On Tue, Aug 24, 2004 at 10:48:14AM +0100, Ian Thurlbeck wrote:
> 
>>What on earth could be writing up to 3GB of data to the drive ?
>>As before the usual suspects of kjournald, kupdated, bdflush and
>>nfsd turn up on the process list.
>>
>>Just how big is the nfs write cache on a typical server ?
> 
> 
> It can be most of RAM.
> 
> 
>>Is it
>>writing the whole lot one go ?
> 
> 
> It might be.  What ratio of COMMIT to WRITE calls are you
> seeing in nfsstat?  Does the export have "sync" or "async"
> in its options?
> 
> Greg.

Greg

Server stats since reboot Monday morning.  It is lightly
loaded mostly:

Server nfs v3:
null       getattr    setattr    lookup     access     readlink
85912   2% 1626277 46% 12375   0% 135833  3% 1295417 36% 773     0%
read       write      create     mkdir      symlink    mknod
136099  3% 151569  4% 7899    0% 64      0% 194     0% 0       0%
remove     rmdir      rename     link       readdir    readdirplus
6270    0% 37      0% 2931    0% 969     0% 266     0% 4893    0%
fsstat     fsinfo     pathconf   commit
1508    0% 890     0% 0       0% 41205   1%

So that's about 4 writes for every commit.

File system export:

/export/raid50  @unix(rw,sync,no_wdelay,hide,nocrossmnt,secure,root_squash,
no_all_squash,subtree_check,secure_locks,mapping=identity,
anonuid=-2,anongid=-2)

I've got Neil's script running to correlate disk writes with
nfs ops and these slowdown event times.  I'll post the results
in a day or so.

Thanks

Ian
-- 
Ian Thurlbeck                http://www.stams.strath.ac.uk/
Statistics and Modelling Science, University of Strathclyde
Livingstone Tower, 26 Richmond Street, Glasgow, UK,  G1 1XH
Tel: +44 (0)141 548 3667           Fax: +44 (0)141 552 2079



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