Question regarding mmap on ZFS, or possibly Dovecot
Kris Kennaway
kris at FreeBSD.org
Sun May 11 07:47:02 UTC 2008
Svein Skogen wrote:
> I still get massive file corruption when allowing Dovecot to run win
> mmap enabled on ZFS/FreeBSD RELENG_7 (as of one week ago), and I have
> seen symptoms of corruption with Samba and mmap on ZFS (although I
> cannot say with certainty that those samba files were corrupted in the
> FreeBSD end, they may have been mangled by my less-than-trustworthy
> windows).
>
> For dovecot+mmap+zfs I get a googlefull of results, same with
> samba+mmap+zfs.
>
> The question remains the same, however. Is this a problem with
> samba/dovecot using mmap incorrectly, a problem with ZFS as such, or a
> problem with the FreeBSD implementation of ZFS? I'm not asking this to
> have someone to point fingers at, but because I want to do some
> risk-reducing activities. If the problem is in the applications,
> disabling mmap in those applications will be a workaround. If the
> problem is with ZFS itself, or with FreeBSD, things start to get
> interesting (it would need some global switch to turn mmap off, and I'm
> not sure such a thing is practical/possible).
I think it's a known but outstanding bug in ZFS + mmap.
Kris
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