question about mksnap_ffs and NFS interaction

antenneX antennex at swbell.net
Sun May 1 05:39:08 PDT 2005


----- Original Message ----- 
From: "Alan Horn" <ahorn at deorth.org>
To: <freebsd-questions at freebsd.org>
Sent: Sunday, May 01, 2005 5:44 AM
Subject: question about mksnap_ffs and NFS interaction


>
> Folks,
>
> I have some NFS exported filesystems (home directories) that I'm
placing
> under snapshots.
>
> Timing of making a snapshot on a 140GB filesystems running about 90%
full
> takes about 17 seconds.
>
> Given that these filesystems are fairly heavily used homedir
filesystems,
> what is the expected impact of those 17 seconds on NFS clients.
>
> My guess is that its enough to be seen but not enough to cause NFS
> timeouts. So far I've been scheduling snapshots for the middle of the
> night, but I'd like to start doing four per day. Does anyone have any
data
> on the likely impact ?
>
> Please reply direct to me as I'm not subbsed to the list.
>
> Cheers,
>
> Al
>

Glad to see a question on this subject and my reply is just more
questions rather than an answer.

I've just moved to 5.4RC3 & read most of the docs and this snap issue is
new to me too. Howe are you scheduling? I noticed I never got a snapshot
until I ran the command to do snaps on each FS. So, I scheduled one for
"noon" as a cron job. Now I get a regular "snap" plus the "nooner", but
they show a random time & both done about the same time.

A mystery to me so far... sure like the new snap feature though.



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