Re: [linux-lvm] JFS or XFS

[Heinz Mauelshagen <mauelshagen@redhat.com>]

On Thu, Jan 15, 2004 at 07:29:08PM -0500, Rajesh Saxena wrote:
> Thank you all for the replies regarding ReiserFS....... I will have to
> do more research into this matter because originally I did not consider
> reiser for the server. It is always good to get other peoples opinions
> on topics like this. I have one small request if you don't mind. The
> mail server will run cyrus imapd and while reading the documentation I
> saw the following note which is attached below after my email. The
> author of this document also notes that XFS includes a program called
> xfs_freeze which will freeze a filesystem from new changes so a more
> reliable snapshot can be created. Again people here with more
> experience with LVM and reiserfs might know of a better way to do the
> snapshot for backups. Any opinions?
> Thank you all for your insight. Please keep posting if you have
> different opinionss.
> 
> Please scroll all the way to the bottom:
> http://acs-wiki.andrew.cmu.edu/twiki/bin/view/Cyrus/Backup
> 
> One issue you may run into: if you're using ReiserFS, at least on Linux
> 2.4 with LVM1, then snapshots may occasionally fail. The snapshot will
> be created fine, but the ReiserFS fileystem on it will not be mountable
> if it has incomplete transactions. The ReiserFS code tries to replay
> the transactions, fails because the snapshot is read-only, and fails to
> mount the FS. I've found that syncing the disks before taking the
> snapshot reduces the chances of this happening dramatically:

Rajesh,

you need to apply the VFS-Lock patch from our web site to avoid your
following 'trick'. That enables LVM to 'flush' all pending fs io
before activating the snapshot.

Another option is to try out LVM2/device-mapper which
supports writable snapshots :)

Regards,
Heinz    -- The LVM Guy --

> 
> sync && sleep 1 && sync && sleep 1 && sync # try to make sure FS will
> be clean
> nice -n -19 lvcreate -s -L 1G -n var_s /dev/OS/var >&/dev/null || \
>   ( echo "Error creating snapshot of /var: $?" && exit 1 )
> 
> 
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*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
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