On Monday 23 December 2019 23:51:11 Gene Heskett wrote:
> On Monday 23 December 2019 21:16:26 Nathan Stratton Treadway wrote:
> > On Sun, Dec 22, 2019 at 11:47:21 -0500, Gene Heskett wrote:
> > > The first, /dev/sda contains the current operating system. This
> > > includes /usr/dumps as a holding disk area.
> > >
> > > The next box of rust, /dev/sdb, is the previous os, kept in case I
> > > need to go get something I forgot to copy over when I first made
> > > the present install. It also contains this /user/dumps directory
> > > but currently unused as it normally isn't mounted.
> > >
> > > Wash, rinse and repeat for /dev/sdc. normally not mounted.
> >
> > [...]
> >
> > > What would be the effect of moving from a single holding area on
> > > /dev/sda as it is now operated, compared to mounting and using the
> > > holding directorys that already exist on /dev/sdb and /dev/sdc?
> > > Seems to me this
> >
> > Right... mount the sdb and sdc holding-disk filesystems, then add
> > additional holdingdisk{} definitions pointing to those directories
> > to your amanda.conf.
> >
> > > should result in less pounding on the /dev/sda seek mechanism
> > > while backing up /dev/sda as it would move those writes to a
> > > different spindle, with less total time spent seeking overall.
> > >
> > > Am I on the right track? How does amanda determine which holding
> > > disk area to use for a given DLE in that case?
> >
> > Yes, I think that's the right track.
> >
> > I have not investigated this in depth, but as far as I know Amanda
> > doesn't have a way to notice that a particular DLE is on physical
> > device local-sda and that a particular holding-disk directory is
> > also on that same physical device, and thus choose to use a
> > different holding disk for that particular DLE. (It does attempt to
> > spread out temporary files across the various holding-disk
> > directories -- it just presumably can't take into account the
> > physical device origin of a particular DLE when decided where to
> > send that DLEs temporary file.)
> >
> > So if you left your existing holding-disk definition as well as
> > adding the ones for sdb and sdc, about one third of the time
> > (theoretically) Amanda would end up using sda for the holding disk
> > for the
> > os-files-on-sda's DLE, and you'd end up with some thrashing. As far
> > as I know, the only way to completely avoid that is to to remove the
> > holdingdisk section pointing to sda from the config and use only the
> > other two.
> >
> > However, as long as you are using more than two dumpers in your
> > config, I'm pretty sure that having more than two physical drives in
> > use for holding disks will still come out ahead, because there will
> > also be some thrashing between the holding-disk files for different
> > DLEs that are being backed up in parallel. So unless the server's
> > sda DLE was a huge portion of the overall data being backed up
> > across your entire disklist, I'd guess that the occasional thrashing
> > on sda when backing up that DLE is a price worth paying to have the
> > holdingdisk activity spread across as many physical drives as
> > possible.
> >
> > (Of course it wouldn't be a bad idea to try it for a dumpcycle with
> > three holding-disk drives and then comment out the entry for the
> > holding disk on sda and try that for a few runs at least and see how
> > the performance compares in reality on your actual installation...)
> >
> >
> > Nathan
>
> Sounds good, so I'll try it.
Except when I mouunted the sdc, it turned out to be the old 1T
for /amandatapes, and its to close to launch time to go thru all the
formatting. So we'll try with 1 holding disks, removeing /dev/sda.
> Also, where is the best explanation
> for "bumpmult"? I don't seem to be getting the results I expect.
>
> Merry Christamas everybody.
>
> > --------------------------------------------------------------------
> >-- ------ Nathan Stratton Treadway - [email protected] -
> > Mid-Atlantic region Ray Ontko & Co. - Software consulting services
> > -
> > http://www.ontko.com/ GPG Key:
> > http://www.ontko.com/~nathanst/gpg_key.txt ID: 1023D/ECFB6239 Key
> > fingerprint = 6AD8 485E 20B9 5C71 231C 0C32 15F3 ADCD ECFB 6239
>
> Copyright 2019 by Maurice E. Heskett
> Cheers, Gene Heskett
Copyright 2019 by Maurice E. Heskett
Cheers, Gene Heskett
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