[patch] giant-less quotas for UFS

[Nicolas KOWALSKI]

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:
>>>>>> 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.

Ok, I'll check with that. Thanks.

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

Yep, it's planned, but only in a few months, when all
students/teachers will go to the beach. ;-)

Just for my knowledge, what will improve the situation ? Better
Locking ? If I read the start of the thread, it looks like the actual
quotas system is still under the giant lock, so...

-- 
Nicolas