Jeff Breidenbach wrote:
Hi all,
[...]
So - I'm thinking of the following backup scenario. First, remount /dev/md0 readonly just to be safe. Then mount the two component paritions (sdc1, sdd1) readonly. Tell the webserver to work from one component partition, and tell the backup process to work from the other component partition. Once the backup is complete, point the webserver back at /dev/md0, unmount the component partitions, then switch read-write mode back on.
Isn't this just the sort of scenario LVM snapshots are meant for ? It might not help with the duration aspect, but it will mean your services aren't down/non-redundant for the entire time it takes to backup.
Everything on this system seems bottlenecked by disk I/O. That includes the rate web pages are served as well as the backup process described above. While I'm always hungry for perforance tips, faster backups are the current focus. For those interested in gory details such as drive types, NCQ settings, kernel version and whatnot, I dumped a copy of dmesg output here: http://www.jab.org/dmesg
I think this might be one of those situations where SCSI really does offer a significant performance advantage, although if you're actually filling up that 500G, it'll be a quite a bit more expensive.
See if you can get hold of a reasonably sized array using SCSI drives and do some comparitive benchmarking.
You might also want to experiment with different filesystems, although that may not be feasible...
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