[linux-lvm] OK to backup physical volume to tape?
mits at xenotrope.com
Sat Dec 30 00:59:39 UTC 2000
Thank you for your suggestions. I forgot to mention some more details:
1. A given day's backup must use only one tape (backup can't span
multiple tapes; I don't have a tape autoloader).
2. Much of the data is already compressed, so additional compression
I have to backup two directories of, say, 60 and 70 GB using a tape
drive with 33 GB native capacity. I was hoping to create the
directories out of smaller PVs that could fit on tape (but I guess I'm
out of luck). I was wondering if I could uses LVM snapshots to solve my
problem, but the same issues still apply.
I think I may have to forget about LVM and divide the 130 GB space into
slices that can fit on tape.
Steven Lembark wrote:
> Mits Yanagihashi wrote:
> > Hello,
> > I'm a LVM newbie with a question. I haven't managed to find an answer
> > yet, so I'm posting my question here.
> > I have a hardware RAID 5 volume on my server; Linux sees this as one 130
> > GB disk (/dev/sda).
> > I have one tape drive that can store 33 GB (uncompressed). I want to
> > backup 130 GB over a 5 day week. I want my users to see two directories
> > "/dir1" and "/dir2", but my tape cannot fit a full dump of either one
> > directory.
> > This is what I want to do:
> > 1. Divide /dev/sda into 5 partitions of 26 GB each. Make each partition
> > a physical volume.
> > 2. Make one volume group. Add two logical volumes (that together use
> > the 5 physical volumes) to the volume group.
> > 3. My users can use the two logical volumes (dir1 and /dir2, which may
> > be 52 and 78 GB respectively). Each night a full backup of one physical
> > volume, and incrementals of the other four physical volumes are written
> > to tape. One tape can store 26 GB, and still have space for incremental
> > backups of the other physical volumes.
> > My question is, is it safe to backup the physical volume (i.e. dump
> > /dev/sda1 to tape)? Or are there complications with file system
> > state/meta information?
> backing up physical volumes is suicide. dd is the only tool that will
> copy the stuff out and it cannot verify the output. better way to fit
> daily backups is zip them or restrict the number of files backed up
> by directory, or simply store the backups on mutiple tapes.
> make incremental backups:
> find /dir1 -mtime -1 |
> cpio -o -Hcrc --file=/dev/tape --io-size=$((1024*1024*16));
> this is the safest way, and if it runs over one tape
> then you will be asked to place in another tape and
> keep going. viola, multiple tape backup sets.
> zip the dailys (not a good idea for long-term storage but quite
> workable for q&d backups, also speeds up recovery:
> find /dir1 | cpio -o -Hcrc | gzip --fast |
> dd of=/dev/tape obs=16386k;
> if you need to REALLY squish the stuff:
> ... | bzip -9 | ...
> ... | gzip --best | ...
> will maximize the compression.
> if people are paranoid about loosing work you can also make
> since-the-weekly-backup incrementals:
> touch start-of-weekly-backup-file;
> then daily:
> find /dir1 -newer start-of-weekly-backup-file |
> cpio -o -Hcrc | blah | blah | blah;
> this will make successively larger backups each day.
> if you use the "--file" option then when one tape runs out cpio
> will rewind and ask you to hit return when the second tape is
> loaded. dd will not support multiple tapes.
> you can also find /dir1/foo onto one backup, find /dir1/bar
> onto another, etc.
> Steven Lembark 2930 W. Palmer St.
> Chicago, IL 60647
> lembark at wrkhors.com 800-762-1582
> linux-lvm mailing list
> linux-lvm at sistina.com
Mits Yanagihashi, Consultant, Xenotrope, Inc.
55 John Street, New York, NY 10038
mits at xenotrope.com http://www.xenotrope.com
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