xfs_freeze is a userspace program included in the xfsprogs rpm. It does run
on Redhat 7.3 (the SGI supplied kernels and userspace for RedHat 7.3 are
somewhat dated; I'd suggest patching the 2.4.21 kernel with XFS 1.3.1
patches and upgrading the userspace programs from the SRPMS). Post to the
linux-xfs mailing list if you need further guidance (lots of people seem to
still run XFS on Redhat 7.3).

> -----Original Message-----
> Sent: Thursday, October 30, 2003 12:28 PM
> Subject: Re: [linux-lvm] RE: [ADMIN] [PERFORM] backup/restore 
> - another
> Does xfs_freeze work on red hat 7.3?
> Cynthia Leon
> -----Original Message-----
> From: Murthy Kambhampaty [mailto:[EMAIL PROTECTED]
> Sent: Friday, October 17, 2003 11:34 AM
> To: 'Tom Lane'; Murthy Kambhampaty
> Cc: 'Jeff'; Josh Berkus; [EMAIL PROTECTED];
> Subject: [linux-lvm] RE: [ADMIN] [PERFORM] backup/restore - another
> area.
> Friday, October 17, 2003 12:05, Tom Lane 
> [mailto:[EMAIL PROTECTED] wrote:
> >Murthy Kambhampaty <[EMAIL PROTECTED]> writes:
> >> ... The script handles situations
> >> where (i) the XFS filesystem containing $PGDATA has an 
> >external log and (ii)
> >> the postmaster log ($PGDATA/pg_xlog) is written to a 
> >filesystem different
> >> than the one containing the $PGDATA folder.
> >
> >It does?  How exactly can you ensure snapshot consistency between
> >data files and XLOG if they are on different filesystem
> Say, you're setup looks something like this:
> mount -t xfs /dev/VG1/LV_data /home/pgdata
> mount -t xfs /dev/VG1/LV_xlog /home/pgdata/pg_xlog
> When you want to take the filesystem backup, you do:
> Step 1:
> xfs_freeze -f /dev/VG1/LV_xlog
> xfs_freeze -f /dev/VG1/LV_data
>       This should finish any checkpoints that were in 
> progress, and not
> start any new ones
>       till you unfreeze. (writes to an xfs_frozen filesystem 
> wait for the
> xfs_freeze -u, 
>       but reads proceed; see text from xfs_freeze manpage in postcript
> below.)
> Step2: 
> create snapshots of /dev/VG1/LV_xlog and /dev/VG1/LV_xlog
> Step 3: 
> xfs_freeze -u /dev/VG1/LV_data
> xfs_freeze -u /dev/VG1/LV_xlog
>       Unfreezing in this order should assure that checkpoints 
> resume where
> they left off, then log writes commence.
> Step4:
> mount the snapshots taken in Step2 somewhere; e.g. /mnt/snap_data and
> /mnt/snap_xlog. Copy (or rsync or whatever) /mnt/snap_data to 
> /mnt/pgbackup/
> and /mnt/snap_xlog to /mnt/pgbackup/pg_xlog. Upon completion, 
> /mnt/pgbackup/
> looks to the postmaster like /home/pgdata would if the server 
> had crashed at
> the moment that Step1 was initiated. As I understand it, 
> during recovery
> (startup) the postmaster will roll the database forward to this point,
> "checkpoint-ing" all the transactions that made it into the 
> log before the
> crash.
> Step5:
> remove the snapshots created in Step2.
> The key is 
> (i) xfs_freeze allows you to "quiesce" any filesystem at any 
> point in time
> and, if I'm not mistaken, the order (LIFO) in which you 
> freeze and unfreeze
> the two filesystems: freeze $PGDATA/pg_xlog then $PGDATA; 
> unfreeze $PGDATA
> then $PGDATA/pg_xlog.
> (ii) WAL recovery assures consistency after a (file)sytem crash.
> Presently, the test server for my backup scripts is set-up 
> this way, and the
> backup works flawlessly, AFAICT. (Note that the backup script starts a
> postmaster on the filesystem copy each time, so you get early 
> warning of
> problems. Moreover the data in the "production" and "backup" 
> copies are
> tested and found to be identical.
> Comments? Any suggestions for additional tests?
> Thanks,
>       Murthy
> PS: From the xfs_freeze manpage:
> "xfs_freeze suspends and resumes access to an XFS filesystem (see
> xfs(5)). 
> xfs_freeze halts new access to the filesystem and creates a 
> stable image
> on disk. xfs_freeze is intended to be used with volume managers and
> hardware RAID devices that support the creation of snapshots. 
> The mount-point argument is the pathname of the directory where the
> filesystem is mounted. The filesystem must be mounted to be 
> frozen (see
> mount(8)). 
> The -f flag requests the specified XFS filesystem to be 
> frozen from new
> modifications. When this is selected, all ongoing transactions in the
> filesystem are allowed to complete, new write system calls are halted,
> other calls which modify the filesystem are halted, and all 
> dirty data,
> metadata, and log information are written to disk. Any process
> attempting to write to the frozen filesystem will block 
> waiting for the
> filesystem to be unfrozen. 
> Note that even after freezing, the on-disk filesystem can contain
> information on files that are still in the process of unlinking. These
> files will not be unlinked until the filesystem is unfrozen or a clean
> mount of the snapshot is complete. 
> The -u option is used to un-freeze the filesystem and allow operations
> to continue. Any filesystem modifications that were blocked by the
> freeze are unblocked and allowed to complete."
> _______________________________________________
> linux-lvm mailing list
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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