On Thu, Oct 20, 2011 at 9:52 AM, ken gebser@mousecar.com wrote:

Though I've worked with enterprise systems, I'm not familiar with FOOS backup software.  Which of those recommended would allow me to backup a system while users are active on it?  If it matters the system uses LVM.    I'd also like to be able to avoid needing the network if possible. That is, I'd plug in a disk into a USB port and backup the system onto that... again, while the system is live.

It is rare for linux applications to lock files, so almost all backup tools will work on an active system, catching the files in whatever state happens to appear in the filesystem. However, database-type applications will have their own requirements to preserve consistency across tables in the snapshot.

Tar/dump/cpio/rsync are all good for copying data. If you want something that can completely reconstruct your system, look at http://rear.sourceforge.net/ (also in EPEL) which should meet you need exactly. But, anytime someone mentions backups, I like to plug backuppc. It does use the network (and another machine) and it won't restore a bootable disk, but it generally takes care of itself and makes sure you always have backup copies with little effort. (http://backuppc.sourceforge.net/ and EPEL).

On Thu, Oct 20, 2011 at 10:52 AM, ken gebser@mousecar.com wrote:

Though I've worked with enterprise systems, I'm not familiar with FOOS backup software.  Which of those recommended would allow me to backup a system while users are active on it?  If it matters the system uses LVM.    I'd also like to be able to avoid needing the network if possible. That is, I'd plug in a disk into a USB port and backup the system onto that... again, while the system is live.

Thanks much.

Others have said that file are not locked on Linux, so you can back them up anyway, but this is surely not your point.

The only way to get a consistent backup is to create a snapshot and back that up. If this is a VM you should be able to make a snapshot and then back up the VM files. LVM is a good way to do it on both physical and virtual machines, but there are a few caveats:

- You need free PEs on the volume group. When you make an LVM snapshot it needs this extra space to store the changed blocks while the snapshot is in existence. Most default LVM installs do not reserve spare PEs for this. The amount of free PEs you need is completely dependent on how many changes get made to the volume while the snapshot exists. If you run out of PEs, the behavior is undefined.

- There is a huge performance penalty. As long as any snapshot exists, there is at least a 50% performance hit. If this is a high performance database server, you might not be able to afford it. Make sure to do your backup on slow times.

The howtoforge link seems to cover most of the mechanics.

-☙ Brian Mathis ❧-