Date: Mon, 25 Jan 2010 00:38:18 +0200 From: Aragon Gouveia <aragon@phat.za.net> To: freebsd-stable@freebsd.org Subject: Re: immense delayed write to file system (ZFS and UFS2), performance issues Message-ID: <4B5CCBDA.3090403@phat.za.net> In-Reply-To: <4B54C100.9080906@mail.zedat.fu-berlin.de> References: <4B54C100.9080906@mail.zedat.fu-berlin.de>
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On 01/18/10 22:13, O. Hartmann wrote: > Symptome: All boxes have ZFS and UFS2 filesystems. Since two weeks or > so, sometimes the I/O performance drops massively when doing 'svn > update', 'make world' or even 'make kernel'. It doesn't matter what > memory and how many cpu the box has, it get stuck for several seconds > and freezing. On the UP box, this is sometimes for 10 - 20 seconds. > A very interesting phenomenon is the massively delayed file writing on > ZFS filesystems I realise. Editing a file in 'vi' running on one XTerm > and having in another Xterminal my shell for compiling this file, it > takes sometimes up to 20 seconds to get the file updated after it has > been written. It's like having an old, slow NFS connection with long > cache delays. > These massively delayed file transactions are not necessarely under > heavy load, sometimes they occur in a relaxed situation. They seem to > occur much more often on the UP box than on the SMP boxes, but this > strange phenomenon also occur on the Dell Poweredge II, which has 16GB > RAM and summa summarum 16 cores. This phenomenon does occur on ZFS- and > UFS2 filesystems as well. It is hardly reproducable. I'm experiencing the same thing, except in my case it's most noticeable when writing to a USB flash drive with a FAT32 filesystem. It slows the entire system down, even if the data being written is coming from cache or a memory file system. I don't know if it's related. I'm running 8-STABLE from about 4 December. Regards, Aragon
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