[patch] giant-less quotas for UFS

[Eric Anderson]

Nicolas KOWALSKI wrote:
> Eric Anderson <anderson at centtech.com> writes:
> 
>> Nicolas KOWALSKI wrote:
>>> Eric Anderson <anderson at centtech.com> writes:
>>>
>>>> Nicolas KOWALSKI wrote:
>>>>> Eric Anderson <anderson at centtech.com> writes:
>>>>>
>>>>>> Nicolas KOWALSKI wrote:
>>>>>>> Yes, this is exactly what is happening. To add some precision, some
>>>>>>> students here use calculation applications
>>>>>>> that allocate a lot of disk space, ususally more than their allowed
>>>>>>> home quotas; when by error they launch these apps in their home
>>>>>>> directories, instead of their workstation dedicated space, it makes
>>>>>>> the server go to its knees on the NFS client side.
>>>>>> When you say 'to it's knees' - what do you mean exactly?  How many
>>>>>> clients do you have, how much memory is on the server, and how many
>>>>>> nfsd threads are you using?  What kind of load average do you see
>>>>>> during this (on the server)?
>>>>> Sorry for the imprecision.
>>>>> The server is a Dual-Xeon 2.8Ghz, 2GB of RAM, using SCSI3 Ultra320
>>>>> 76GB disks and controller. It is accessed by NFS from ~100 Unix
>>>>> (Linux, Solaris) clients, and by Samba from ~15 Windows XP. The
>>>>> network connection is GB ethernet.
>>>>> During slowdowns, it's only from a NFS client view that the server
>>>>> does not respond. For example, a simple 'ls' in my home directory is
>>>>> almost immediate, but when it slows down, it can take up to 2 minutes.
>>>>> On the server, the load average goes to 0.5, compared to a default
>>>>> maximum of 0.15-0.20. The nfsd processus shows them in the state
>>>>> "biowr" in top, but nothing is really written, because the quotas
>>>>> system block any further writes to the user exceeding her/his quotas.
>>>>>
>>>> In this case (which is what I suspected), try bumping up your nfsd
>>>> threads to 128.  I set mine very high (I have around 1000 clients),
>>>> and I can say there aren't really ill-effects besides a bit of memory
>>>> usage (which you have plenty of).  I suspect increasing the threads
>>>> will neutralize this problem for you.
>>> Using 128 nfsd threads, I stressed the server, by running on a NFS
>>> client a small C program, writting continuously in a file, so that the
>>> user "biguser" (account stored on /export/home2) exceeds his quota.
>>> It half-works: during the test, users working on another disk
>>> (/export/home) did not see any difference, but users working on the
>>> same disk that "biguser" (/export/home2) where almost halted.
>>> So, this is better, because before everybody was halted, but there is
>>> still a problem.
>>> Any other tips ?
>> Watch gstat during the testing, and see if the disk that holds the
>> full partition is really busy.  I'm betting it's thrashing the disk
>> continually checking for free space.  I don't think there's any way to
>> avoid that.
> 
> Mh, I did not find this "gstat" tool on the system or in the ports;
> perhaps is it in >= 5.x ? (the server is running 4.11-p15).
> 
> It is sad I can not do anything about it: such a server pulled down by
> a single NFS-client. :-(


*sigh* - I should really pay more attention to the beginning of the 
thread.  I thought you were on 5.x, so my mistake.  You'll need to use 
iostat to see what's busy with your disks.

I strongly recommend going to 6.x if you can..

Eric



-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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