[BBLISA] rsync vs dump for in-use files?

[Edward Ned Harvey]

In-use files on Linux, you can't do anything at all.  I suppose you could
attempt LVM snapshots, but that's crappy at best.

For in-use file backup, I recommend either a Netapp, or some other device
with a file system more intelligent than EXT3, which is able to do
filesystem snapshots (this is much better than a block-level LVM snapshot.)

Imagine you have a program, such as mysqld, which opens files read-write,
and keeps them that way through the entire operation of the process.  At no
time is a complete file ever written, and at no time is the file ever
closed.  It is 100% impossible to backup that file, any more recently than
it was opened.  But filesystems that do snapshotting (ZFS, Netapp, some
others) can at least allow you to backup  the file as it was, just before
the most recent time it was opened.

No matter what you do, if people (or processes) keep their files open
indefinitely and never close, the most recent changes to that file are at
risk.  It's a problem that IT people must face, but not solve.




> -----Original Message-----
> From: bblisa-bounces at bblisa.org [mailto:bblisa-bounces at bblisa.org] On
> Behalf Of Scott Ehrlich
> Sent: Saturday, September 29, 2007 9:04 PM
> To: bblisa at bblisa.org
> Subject: [BBLISA] rsync vs dump for in-use files?
> 
> I'd like to get list consensus for which method of file
> preservation/backup
> does better for files in-use?  This will be on a RHEL 5 server.
> 
> Thanks.
> 
> Scott
> 
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