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Re: Slow restore using NetVault backup application

To: Sherman Boyd <meekrob@xxxxxxxxxxx>
Subject: Re: Slow restore using NetVault backup application
From: Stephen Lord <lord@xxxxxxx>
Date: 13 Nov 2002 17:23:05 -0600
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <1037225493.3dd2ce15cb6c2@meth.gravital.net>
References: <1037225493.3dd2ce15cb6c2@meth.gravital.net>
Sender: linux-xfs-bounce@xxxxxxxxxxx
On Wed, 2002-11-13 at 16:11, Sherman Boyd wrote:
> Hi,
> 
> I've been using the NetVault backup application to back up my Linux boxes 
> running XFS over the network.  Everything is very fast, except restores crawl 
> along at about 21 kb per second.  The guys at NetVault said that it was 
> because 
> I have a journaling filesystem, and suggested that I turn off journaling (if 
> possible) while I am restoring a backup. This seems strange to me and brings 
> up 
> some questions:

Maybe it is because netvault does not know how to use a journalling
filesystem. Unless we know how it is writing data into the filesystem
I am not sure we can do much here. My bet is that it is opening files
O_SYNC and doing small writes. You could attach strace to the process
doing the writing (or one of them) and send a sample of its output.

> 
> 1) Does anyone else experience this kind of an issue using any other backup 
> application?
> 
> 2) Can I turn off journaling in XFS temporarily to resolve this, and would I 
> want to?

No you cannot.

> 
> 3) Why would journaling affect the speed of restores and not backups?
> 

backup is a readonly operation, restore is a write operation, only 
the latter involves the journal.

> Thanks for reading this and thanks to those that develop XFS,
> 
> Sherman Boyd
> meekrob@xxxxxxxxxxx
> 

Steve



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