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Re: [BackupPC-users] how to backup the backuppc server (off site)
2009-02-15 15:13:57
If you are using linux software raid you will find that the the raidset will tend to read and write to the first disk in the raid set first.
you can have a raid1 as /dev/md0 including devices /dev/sda1 and /dev/etherd/e0.1 and the md0 device will use the first device in the list as the primary read and write and THEN write to the second member.
This can somewhat hide the latency that you are worried about. though as some point the buffer will be full the md0 device will wait for the second device to sync.
the other option in this setup would be to have md0 have 1 active member and then add another device when you want to sync the backup. Unfortunately this is a block for block rebuild so it can take quite a long time.
If you plan to do this mirror setup with mdadm on linux I suggest that you rotate 2 disks for the mirror so that one is always in the backuppc server and you just swap them out. You can have mdadm auto-assemble based on the superblock on the drive so if the drive has ever been part of that raidset it will import quite easily with a udev script.
You also need to be sure to change the raid rebuild speed limit in /proc/sys/devices/raid/rebuild_min_speed (i think, typing from memory) else the rebuild will will be very slow. If you eliminate the limit you can expect 1/2 the peak transfer speed of the drive, maybe more. 1TB may take 5-10 hours to rebuild the mirror.
I have found that it is better to run multiple backuppc servers rather than try to scale up to many TB of data. It is much faster to do restores, shortens the nightly process by parrelizing the backups, and keeps the concurrent backups/spindle low. plus it allows much faster disk mirroring.
One other option is that you can run 2 drives in a mirror and have the ability to take 1 drive offline make an image from it, then add it back to the mirror. Then you never even shutdown backuppc.
On Wed, Feb 11, 2009 at 3:01 AM, Tino Schwarze <backuppc.lists AT tisc DOT de> wrote:
On Wed, Feb 11, 2009 at 03:33:05AM -0600, mortonda AT dgrmm DOT net wrote:
> > 1) AoE (ATA over Ethernet) - you could add a drive to your BackupPC
>
> > 2) (Soft?)RAID1 with at least 3 drives. I've used this and I'm currently
>
> 1 + 2 = 4) RAID over the network. See http://www.drbd.org/
latency to the filesystem BackupPC is running on since it's VERY I/O
intensive. I've never used/tested DRDB though, just saw it on a
customer's server where speed isn't main priority.
Would you run a database on DRDB?
Bye,
Tino.
--
"What we nourish flourishes." - "Was wir nähren erblüht."
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