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Does anyone on this mailing list have an idea what went wrong with
ZFS and Cyrus IMAP? Here's an excerpt that explains the problem:
About a week before classes actually start is when all the kids start
moving back into town and mailing all their buds. We saw process
numbers go from 500-ish to as high as 5,000. Load would climb
radically after passing 2,000 processes and systems became slow to
respond.
Here's a suggestion on the cause:
The root problem seems to be an interaction between Solaris' concept
of global memory consistency and the fact that Cyrus spawns many
processes that all memory map (mmap) the same file. Whenever any
process updates any part of a memory mapped file, Solaris freezes all
of the processes that have that file mmaped, updates their memory
tables, and then re-schedules the processes to run. When we have
problems we see the load average go extremely high and no useful work
gets done by Cyrus.
I'm concerned because I'm also using Cyrus IMAP with ZFS. So far,
it's been extremely well behaved. Snapshots are one the best parts of
this system.
--
-Gary Mills- -Unix Support- -U of M Academic Computing and Networking-
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