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Date:      Fri, 01 Sep 2006 16:06:01 -0700
From:      Skylar Thompson <skylar@cs.earlham.edu>
To:        Kris Kennaway <kris@obsecurity.org>
Cc:        Paul Lathrop <plathrop@squaretrade.com>, freebsd-questions@freebsd.org
Subject:   Re: Snapshot performance
Message-ID:  <44F8BCD9.4090308@cs.earlham.edu>
In-Reply-To: <20060901213936.GA21561@xor.obsecurity.org>
References:  <44F87733.2020405@squaretrade.com> <20060901213936.GA21561@xor.obsecurity.org>

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Kris Kennaway wrote:
> On Fri, Sep 01, 2006 at 11:08:51AM -0700, Paul Lathrop wrote:
>  =20
>> Hi all,
>>
>> We're working on deploying a new mail server on FreeBSD 6.1-STABLE. On=
e
>> of the major selling points was the ability to take filesystem snapsho=
ts
>> in order to make backups from a consistent filesystem on such a
>> high-traffic system. Unfortunately, when I take a snapshot, performanc=
e
>> slows to a crawl - to the point where the system stops responding to
>> network requests (ping, SMTP, etc.). Also, the snapshot takes 10-15
>> minutes to complete.
>>
>> Is this a typical situation? Will I need to schedule downtime for
>> backups in spite of this nifty new feature? Am I doing something wrong=
?
>>    =20
>
> Time depends on the size of the filesystem - but you are correct that
> snapshots were not designed with performance in mind (rather, to speed
> up booting after an unclean shutdown by removing the need to wait for
> fsck).
>
> Kris
>  =20
Are there plans to improve performance of snapshots? Using the
freebsd-snapshot port to link FS snapshots to the automounter is pretty
nifty, but it does kill I/O performance while that's in progress as the
OP mentioned.

--=20
-- Skylar Thompson (skylar@cs.earlham.edu)
-- http://www.cs.earlham.edu/~skylar/



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