[CentOS] your advice on backup procedure

Nataraj incoming-centos at rjl.com
Sat Mar 24 00:24:34 EDT 2012


On 03/23/2012 05:19 PM, Bob Hoffman wrote:
> Hello all,
> I am down to my last hurdle of my project, backups.
> I am thinking of three different ways to go and wanted to ask for input 
> on what you think is the better choice.
> Not asking for 'how to' but more of 'what is best in your experience'
>
> The scenario...
> centos server acting as a virtual host. Virtual machines are webservers 
> and dns servers. All on one machine, all running centos 6.
> Virtual machines are kvm, sitting in lvm storage.
>
> What I want to do..
> auto backups of the virtual machines to be stored on the virtual host's 
> extra drives for later download to my home computer.
>
> Many backup solutions and programs seem centered on a network of 
> computers with file sharing. I do not have this and don't think I want 
> to go that way on my host.
>
>
> My three thoughts, not sure which one to pursue...
> (involves certain folders, /home/ (which includes maildir), /var/www/, 
> /mysqlhotcopys and bin files, and maybe a few more. I can rebuild the 
> comp pretty quick and then restore, or maybe just do one big backup of 
> each server, then work on the folders as a solution)
>
> 1- Amanda. I do not know much about it or how it would deal with mysql 
> databases, but it look promising. I do not have a NFS in place on any of 
> the installs.
>
> 2- rsnyc - some kind of rsync going from the host to each machine, 
> putting it on the host's backup drives. Adding a mysql hotcopy of some 
> kind on the VMs, along with bin files, saved to a special folder that 
> will then be part of the rsync. Once a week full of both rsync and 
> mysqlcopy, then incremental daily.
I think backuppc, syncing over rsync directly to the VM makes sense here.
> 3- Use kpartx ? and access the lvm the VM is on to rsync internally on 
> the host, ditto above with the mysql copy/bin setup.
You can't safely mount the VM's partitions without shutting down the
VM.  You might get away with it with an LVM snapshot taken inside the
host, but that assumes that it's safe to access the LVM datastructure
from outside the VM while the VM is running and it may not be.
> Number 3 seems like it is the securest way, but obviously not much info 
> out there on it.
> Number 2 seems like the 'old way' and will require some real work to get 
> it right
> number 1 looks good, but do not really know anything about it.
For the database you have many options.  I would suggest at least weekly
do this:
1) shutdown the mysql database server
2) take a snapshot of the partition with the mysql database server
3) restart your mysql server (the whole shutdown/snapshot/restart take
less than 15 seconds)
4) Do a full backup of that snapshot, using backuppc, tar, dump or
whatever you choose

In order to do this, you must of course setup the database on an LV
partition (MY LV partition is simply an ext4 or ext 3 partition, mounted
on /var/lib/mysql).  Make sure there is adequate space on your snapshot
LV partition for any data that might get written to the database before
the snapshot gets backuped and deleted.

If your database is small you can do daily backups of the entire
database like this.  Otherwise you can use tools like mysqldump and
mysqlhotcopy, but you should make sure you have a pretty good
understanding of these tools and that you are backing things up properly
with them.

Some people run replication between two database servers and then
shutdown the secondary server and back it up.

There are also backup tools like duplicity and storebackup which I have
recently learned about that are supposed to be able to do incremental
backups of binary files, where you could actually do a restore of the
database from your full backup and then somehow apply an update to the
database files from incrementals.  I have not yet tested this method. 
There again, I would still shutdown/snapshot/restart the mysql server to
ensure database integrity during the backup.

Whatever you choose, I suggest you perform test restores and if you
choose database level backups, make sure you understand what you are
doing and that you are saving the backup in a way that you are able to
recover it.

If you data is important consider doing backing up in two different
formats to 2 different media types.

I think simply doing at least a weekly full backup of the entire
/var/lib/mysql directory (via snapshot or server shutdown) is the least
prone to user error.

Be aware that things like changes in database format, etc can make old
backups difficult or impossible to restore.  Many people, myself
included, ran into some problems when mysql changed the way it handled
character set encodings and it was not so straightforward to restore
mysqldump backups made with an older version of mysql, using the latest
version of mysql.  Many options had to be specified and some people
still had to write scripts to manually go through and make some
conversions.  I ran into these problems while upgrading a mediawiki
database that was running under a very old version of mysql for a client.

So if having long term access to old backups is important, you must
check for compatibility between newer/older versions of mysql and either
do conversion/refresh of your data, or make sure you still have
functional copies of the tools necessary to restore older versions.

Nataraj



> Which way would you go, or do you have a different way you like better?
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