[Duplicity-talk] Duplicity 4.2.1 on CentOS 4.7 causing resource shortage on VPS

[Marcus Clements]

Hi,

I am happily using Duplicity 4.2.1 on my CentOS 4.7 VPS as a scheduled
nightly backup. Here are the statistics from last night (a typical
night):

--------------[ Backup Statistics ]--------------
StartTime 1236141154.58 (Wed Mar  4 04:32:34 2009)
EndTime 1236142613.88 (Wed Mar  4 04:56:53 2009)
ElapsedTime 1459.30 (24 minutes 19.30 seconds)
SourceFiles 274433
SourceFileSize 11725383817 (10.9 GB)
NewFiles 439
NewFileSize 257124568 (245 MB)
DeletedFiles 235
ChangedFiles 1347
ChangedFileSize 447798267 (427 MB)
ChangedDeltaSize 0 (0 bytes)
DeltaEntries 2021
RawDeltaSize 133981593 (128 MB)
TotalDestinationSizeChange 276740588 (264 MB)
Errors 0
-------------------------------------------------

I use munin to monitor the performance of the server in general and
there are no unusual or troubling resource problems reported there.
However in the Virtuozzo control panel, under Quality of Service,
every night during the backup the VPS runs out of lockedpages, which
are (from the Virtuozzo manual) "The memory not allowed to be swapped
out (locked with the mlock() system call), in pages."
This server is relatively new and not under much load currently but
that is likely to change in the coming months. I've talked to the
hosting provider, who doubled the lockedpages parameter a couple of
days ago in response to my request but QoS still repeatedly reports
"Yellow Zone", "Red Zone" and "Black Zone" resource shortages for
lockedpages.

I'm concerned that the backup will make the server run slowly while it
is in operation. Is there a change I can make to the settings in
Duplicity or elsewhere in the system so that the process uses less of
the lockedpages resource?

Thanks in advance

Marcus Clements