Les Mikesell <[email protected]> wrote on 05/24/2011 11:09:09 AM:
> On 5/24/2011 9:36 AM, Timothy J Massey wrote:
> >
> > I ended up upgrading that system to 2GB of RAM merely so that I could
> > finish the fsck.
> >
> > (Oh, and to a long-ago debate about would more RAM help BackupPC to do
> > its job: nope. The backups with 2GB took almost exactly the same
amount
> > of time as the ones with 512MB. I wasn't swapping with 512MB, and
there
> > just isn't that much data that can be profitably cached while doing a
> > backup, as long as the file list can fit in RAM: the few dentries and
> > inodes in use at a time just don't take that much space...)
>
> That just seems wrong - although I'd consider 2Gb to be a fairly small
> amount of RAM and maybe not enough to help. It should be useful to
> cache the whole pool directory tree so you don't have to seek there to
> check for every hash match.
Two things: 1) If *quadrupuling* the total memory does not improve the
performance measurably, it is likely not to be improved with even more,
and 2) your idea of "small" and mine are more than a little different. My
backup servers are a *lot* closer to Jeffrey's plug computer than whatever
you're using. I guess there's a third point: I'm not convinced that I'm
*not* caching the entire pool tree--especially with the 2GB.
I just reviewed my backup server logs. I upgraded the RAM in 2011, and
I've gone back and checked several different monthly logs from 2010: all
of the full backups were within 5% of each other (and usually closer: this
is an effectively static and unused server with 250GB of data and about a
half-million files).
So I just don't see that more RAM is going to help. Period. Of course,
YMMV (especially if you have a truly obscene number of files: many
millions).
By the way, to be clear: BackupPC does an outstanding job even on small
hardware: 1.2GHz VIA CPU, 512MB RAM and a single SATA spindle is my
standard BackupPC appliance (not server: appliance! :) ). While I would
certainly take it, I'm not actually *looking* for more performance. My
fulls take about 400 minutes for servers with 250-500GB of data and
500,000 or so files, and my incrementals take just minutes (15 - 75,
depending on how late in the week/busy the users are).
That's an effective backup rate of 19MB/s (with no small thanks to rsync's
help, too).
Timothy J. Massey
Out of the Box Solutions, Inc.
Creative IT Solutions Made Simple!
http://www.OutOfTheBoxSolutions.com
[email protected]
22108 Harper Ave.
St. Clair Shores, MI 48080
Office: (800)750-4OBS (4627)
Cell: (586)945-8796
------------------------------------------------------------------------------
vRanger cuts backup time in half-while increasing security.
With the market-leading solution for virtual backup and recovery,
you get blazing-fast, flexible, and affordable data protection.
Download your free trial now.
http://p.sf.net/sfu/quest-d2dcopy1
_______________________________________________
BackupPC-users mailing list
[email protected]
List: https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki: http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/
