BackupPC-users

Re: [BackupPC-users] Question about "link pending".

2008-06-02 20:52:30
Subject: Re: [BackupPC-users] Question about "link pending".
From: "Bruno Faria" <brunothebigb AT gmail DOT com>
To: backuppc-users <backuppc-users AT lists.sourceforge DOT net>
Date: Mon, 2 Jun 2008 19:52:22 -0500
Thanks for the help Chris!

* Using the term job loosely here, as I personally have
$Conf{MaxBackupPCNightlyJobs} = 8.

Is backuppc nightly jobs heavy on RAM?

I would like to increase the amount of BackupPC nightly jobs, but right now all of my RAM and most of my swap is being used by BackupPC_Dump.

On Mon, Jun 2, 2008 at 7:32 PM, Chris Robertson <crobertson AT gci DOT net> wrote:
Bruno Faria wrote:
> Hi,
>
> I've posted a similar a question before but since I didn't get any response
> the first time, I guess I'll try again . :)
>

You might be edified by reading the documentation
(http://backuppc.sourceforge.net/faq/BackupPC.html).  I highly recommend
the section detailing how the software works
(http://backuppc.sourceforge.net/faq/BackupPC.html#backuppc_operation).
If you are not the document reading type, I have excerpted some
pertinent details below...

> For some reason I'm getting alot of "link pending". During the first backups
> I didn't have any problem with link pending since once a backup was done it
> would be done without any link pending. But whenever BackupPC_Nightly
> started, all the backups are getting "link pending" for hours and hours
> (about 7+ hours of link pending for each host).
>
> So here are my questions:
>
> 1) Is it normal for links to be pending this long?
>

 From the document section on $Conf{MaxBackupPCNightlyJobs} (under
http://backuppc.sourceforge.net/faq/BackupPC.html#general_server_configuration):

"Each night, at the first wakeup listed in $Conf{WakeupSchedule}
<http://backuppc.sourceforge.net/faq/BackupPC.html#item__conf_wakeupschedule_>,
BackupPC_nightly is run. Its job is to remove unneeded files in the
pool, ie: files that only have one link. To avoid race conditions,
BackupPC_nightly and BackupPC_link cannot run at the same time."

> 2) Would it be bad if I just increase the max amount of "link pending" on
> the config.pl file to allow about 20+ pending links?
>

Personally, I have "$Conf{MaxPendingCmds} = 50;"  My nightly job* (which
removes between 6 and 9 GB of data from  a pool size of about 240GB on a
pair of software mirrored SCSI drives) is currently taking between 9 and
14 hours.  I get close to 30 link jobs queued, and they all clear out
less than an hour after the nightly job finishes.  Since I run all my
backups at night (blackout period of 07:00 to 19:30) I'll probably wind
up making the "nightly" job run in the morning.

> 3) What's the job of "link pending"?
>

Also from the docs :

"BackupPC_link reads the NewFileList written by BackupPC_dump and
inspects each new file in the backup. It re-checks if there is a
matching file in the pool (another BackupPC_link could have added the
file since BackupPC_dump checked). If so, the file is removed and
replaced by a hard link to the existing file. If the file is new, a hard
link to the file is made in the pool area, so that this file is
available for checking against each new file and new backup."

> Thanks for help in advance!
>
> --Bruno

Hope this helps.

Chris

* Using the term job loosely here, as I personally have
$Conf{MaxBackupPCNightlyJobs} = 8.

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