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On 09/01/12 09:00, Les Mikesell wrote:
On Sun, Jan 8, 2012 at 4:48 AM, John Habermann
<jhabermann < at > cook.qld.gov.au> wrote:
You can see that the backup of the /opt share takes nearly the
total time of the incremental taking about 8 and half hours to
complete while the backup of the /opt rsync share in the full
backup takes about 3 and half hours. The full backup is slightly
longer than what it takes if I just do a rsync over ssh copy of
the file from the client server to the backup server.
I have found that rsync seems to always transfer the whole file
when copying this file from the client server to the backup
server: My questions for the list are: 1. Is it reasonable for
rsync to transfer the whole file when copying a large ntbackup
file?
Yes, those files may have little or nothing in common with the
previous copy. If compression or encryption are used they will
ensure that no blocks match and even if they aren't, the common
blocks may be skewed enough that rsync can't match them up.
Definitely, I find that transferring (for example) uncompressed
mysqldump files will transfer less bytes than transferring the
compressed files. (Obviously because the compressed file will transfer
100%, while the uncompressed will only transfer the changes).
2. Why does an incremental backup of this file take so much
longer than a full backup of it or a plain rsync of this file?
That doesn't make sense to me either. Are you sure that is
consistent and not related to something else that might have been
using the link concurrently?
I'm not exactly sure, but I've found the best way to approach these
types of files (any dump/export from another application, MS SQL,
MySQL, custom applications, etc), is to:
1) Ensure the file is uncompressed if it is in plain text format of
some sort, which may mean uncompressing it after the other application
creates it, and before backuppc will see it. The size of chunks can
depend on transfer speeds available, total file size, etc...
2) Any file over about 100M, I split into chunks (using split) of
anything from 20M to 100M chunks. I've found that rsync will transfer
these chunks much more quickly than transferring the whole file. Also,
if the transfer is interrupted (on a full backup), it will save the
backup as a partial, and continue from the last chunk (as opposed to
re-starting that 5G file, you only lose a maximum of 100M).
Regards,
Adam
- --
Adam Goryachev
Website Managers
www.websitemanagers.com.au
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