Extreme performance falling on ZFS by durable operation of a server
Alexandr D. Sergeev
ales at ripn.net
Thu Apr 8 15:43:12 UTC 2010
There are problems with a server on FreeBSD 7.2 CURRENT (6 Jul 2009), carrying out the task of mail server SMTP, IMAP.
Messages are stored in maildirs on file system ZFS (mirror of 2 SAS 3k drives).
Dovecot is used as IMAP server.
After reboot the system works perfectly, however, somewhere in a month, at the same load, arise periodic long delays at opening of new letters.
Judging by output iostat -x -w 1, during these moments the disk subsystem is strongly loaded.
%busy disks comes nearer to 100 %. Readings nearby 300 per sec prevail. and approx. 10MBytes per sec.
Somebody can advise, what diagnostics needed, for understanding of the reason of problems?
There is an opinion that a problem with ZFS.
Probably, it does not have enough memory. Because during the periods of occurrence of a problem, ARC is have less 300MB:
solaris 1245732 274745K - 25872717949 16,32,64,128,256,512,1024,2048,4096
Or it is bug of ZFS implementation.
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