Date: Tue, 11 Apr 2006 06:10:57 -0500 From: Eric Anderson <anderson@centtech.com> To: Nicolas KOWALSKI <Nicolas.Kowalski@imag.fr> Cc: freebsd-fs@freebsd.org Subject: Re: [patch] giant-less quotas for UFS Message-ID: <443B8EC1.8080004@centtech.com> In-Reply-To: <vqoek04vbap.fsf@corbeau.imag.fr> References: <20060329152608.GB1375@deviant.kiev.zoral.com.ua> <vqoy7ydv7lw.fsf@corbeau.imag.fr> <20060410144904.GC1408@deviant.kiev.zoral.com.ua> <vqou091v3vt.fsf@corbeau.imag.fr> <443A7C8E.4020203@centtech.com> <vqopsjpv2ci.fsf@corbeau.imag.fr> <443A8842.6060802@centtech.com> <vqolkudv09k.fsf@corbeau.imag.fr> <443A97F9.8090601@centtech.com> <vqoek04vbap.fsf@corbeau.imag.fr>
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Nicolas KOWALSKI wrote: > Eric Anderson <anderson@centtech.com> writes: > >> Nicolas KOWALSKI wrote: >>> Eric Anderson <anderson@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. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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