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Debian Stretch observations

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From: Juergen Nickelsen <ni@w21.org>
Date: Wed, 19 Jul 2017 09:50:06 +0200

   Hello all,
   
   after upgrading my external (hosted) server to Debian Stretch last weekend, I have noticed that backups with obnams seem to take longer. Where the hourly backup of the home directories (just a handful, and mainly for mail) before took 2 or three minutes, it seems to be at 4 to 6 minutes now.
   
   At the same time I see that the page cache has a size that seems not only excessive (up to 7 of 8 GB RAM, with not more disk I/O than before the upgrade, when it was much smaller), but also seems to actively drive the processes into the swap space, making many operations very slow. This may or may not be the reason for the perceived slowness of the backup.
   
   Now I'd like to try if the backup and other things are faster again with a less excessive page cache size, but all the advice about limiting it that I find on the net seems to be outdated with respect to the 4.9 kernel. Any pointers, perhaps?
   
   Also, apparently there is not yet an obnam repository for Stretch; I get by with an /etc/apt/sources.list.d/obnam.list with
   
   deb http://code.liw.fi/debian unstable main
   
   Regards, Juergen.
From: Jan Niggemann <jn@hz6.de>
Date: Wed, 19 Jul 2017 13:06:38 +0200

   Did you change obnam versions during the upgrade?
   If not, then I make the wild guess that it has to do with the new kernel that stretch installed...
   
   Am 19. Juli 2017 09:50:06 MESZ schrieb Juergen Nickelsen <ni@w21.org>:
   >Hello all,
   >
   >after upgrading my external (hosted) server to Debian Stretch last
   >weekend, I have noticed that backups with obnams seem to take longer.
   >Where the hourly backup of the home directories (just a handful, and
   >mainly for mail) before took 2 or three minutes, it seems to be at 4 to
   >6 minutes now.
   >
   >At the same time I see that the page cache has a size that seems not
   >only excessive (up to 7 of 8 GB RAM, with not more disk I/O than before
   >the upgrade, when it was much smaller), but also seems to actively
   >drive the processes into the swap space, making many operations very
   >slow. This may or may not be the reason for the perceived slowness of
   >the backup.
   >
   >Now I'd like to try if the backup and other things are faster again
   >with a less excessive page cache size, but all the advice about
   >limiting it that I find on the net seems to be outdated with respect to
   >the 4.9 kernel. Any pointers, perhaps?
   >
   >Also, apparently there is not yet an obnam repository for Stretch; I
   >get by with an /etc/apt/sources.list.d/obnam.list with
   >
   >deb http://code.liw.fi/debian unstable main
   >
   >Regards, Juergen.
From: Juergen Nickelsen <ni@w21.org>
Date: Wed, 19 Jul 2017 14:04:26 +0200

   On 19.07.2017 13:06, Jan Niggemann wrote:
   > If not, then I make the wild guess that it has to do with the new kernel
   > that stretch installed...
   
   Yes, that is what I meant. Apart from the repository, that is.
   Regards, Juergen.
From: Andreas Ziegler <ml@andreas-ziegler.de>
Date: Thu, 20 Jul 2017 00:14:16 +0200

   Juergen Nickelsen schrieb am 19.07.2017 um 14:04:
   > On 19.07.2017 13:06, Jan Niggemann wrote:
   >> If not, then I make the wild guess that it has to do with the new kernel
   >> that stretch installed...
   > 
   > Yes, that is what I meant. Apart from the repository, that is.
   > Regards, Juergen.
   
   could you please clarify which obnam version you were using before the
   upgrade and are using now?
   
   shipping with debian, jessie has obnam 1.8 and stretch 1.22
   
   maybe you should try using debian's 1.22 if you're using a non-debian build.
   
   but regardless of this, my experience with obnam is, that it's the most
   ressource-eating backup software i used so far...
   
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From: Juergen Nickelsen <ni@w21.org>
Date: Thu, 20 Jul 2017 06:49:04 +0200

   On 2017-07-20, at 00:14, Andreas Ziegler <ml@andreas-ziegler.de> wrote:
   > 
   >> Yes, that is what I meant. Apart from the repository, that is.
   >> Regards, Juergen.
   > 
   > could you please clarify which obnam version you were using before the
   > upgrade and are using now?
   > 
   > shipping with debian, jessie has obnam 1.8 and stretch 1.22
   > 
   > maybe you should try using debian's 1.22 if you're using a non-debian build.
   
   I seem to have been using obnam 1.22 since June 25, meaning well before the upgrade; as I have thought it was obvious when I mentioned this sources.list snippet, I have been getting obnam directly from code.liw.fi.
   
   But anyway, I didn't want to imply that this issue is in any way *caused* by obnam, rather that obnam is *affected* by it. So, if you haven't seem the same *and* some explanation or remedy for it, we might as well drop the issue.
   
   Regards, Juergen.
From: Andreas Ziegler <ml@andreas-ziegler.de>
Date: Thu, 20 Jul 2017 11:59:13 +0200

   Am 20.07.2017 um 06:49 schrieb Juergen Nickelsen:
   > But anyway, I didn't want to imply that this issue is in any way *caused* by obnam, rather that obnam is *affected* by it. So, if you haven't seem the same *and* some explanation or remedy for it, we might as well drop the issue.
   
   as i'm not yet using stretch (and using the debian supplied packages) i
   cant say that you problem doesnt exist.
   
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