Re: Always fill every tape

[Jason L Tibbitts III]

> "JM" == Jean-Francois Malouin  
> writes:

JM> This is not was I have experienced, at least with 3.3.x.

For the record, my server is 3.5.1.

JM> I've been using the following in some configs with the expected
JM> result:

OK, it's good to know that at some point it's worked for someone.  I was
using "flush-threshold-scheduled 70" and "flush-threshold-dumped 90" but
it would always flush if there was data to flush even if it only filled
a small portion of the tape.  This led to a two-day cycle:

Day 1: Nothing to flush, dump to the holding disk.
Day 2: Flush data from yesterday and write today's dumps to tape,
   filling about 40% of a tape.  Given the thresholds, it should not
   have written anything for one or two more days.
repeat

I've upped those limits to match yours so we'll see what happens after a
few days.

 - J<

Re: Always fill every tape

[Jean-Francois Malouin]

Hi Jason,

* Jason L Tibbitts III  [20180314 11:33]:
> And so it turns out that if you turn off autoflush, Amanda will never
> flush existing dumps to tape regardless of the flush-threshold-*
> settings.  Which I guess makes sense.  And with "autoflush yes", it
> seems to simply flush everything currently on the holding disk
> regardless of other settings.  So as far as I can tell, the
> flush-threshold-* settings are simply not working as designed.
> 
> What can I tweak to get more insight into how Amanda decides when to
> flush existing dumps?  I will continue to play with the thresholds to
> see if I can get behavior closer to I'm looking for but it would be good
> to have some insight into the decision process.
> 
>  - J<

This is not was I have experienced, at least with 3.3.x.
I've been using the following in some configs with the expected result:

flush-threshold-dumped 100
flush-threshold-scheduled 100
taperflush 100
autoflush yes 

As stated in the amanda.conf manpage, those will force amanda to start
writing to a new volume only if the data in the hold disk plus the
scheduled data are at least 100% of the volume capacity.  If anything is
left in the hold disk after a run, it will be flushed the next time
amdump runs. Those constraints only apply when a new volume is
requested.

Note that if you manually flush using amflush, you must override
those values with something like:

amflush -oflush-threshold-dumped=0 -oflush-threshold-scheduled=0 -otaperflush=0 
...

otherwise the flush constraints might not be met and the flush won't
complete entirely or at all.

Of course, I might be wrong so take this with a grain of salt!

cheers,
jf

Re: Always fill every tape

[Jason L Tibbitts III]

And so it turns out that if you turn off autoflush, Amanda will never
flush existing dumps to tape regardless of the flush-threshold-*
settings.  Which I guess makes sense.  And with "autoflush yes", it
seems to simply flush everything currently on the holding disk
regardless of other settings.  So as far as I can tell, the
flush-threshold-* settings are simply not working as designed.

What can I tweak to get more insight into how Amanda decides when to
flush existing dumps?  I will continue to play with the thresholds to
see if I can get behavior closer to I'm looking for but it would be good
to have some insight into the decision process.

 - J<

Re: Always fill every tape

[Jason L Tibbitts III]

> "DSB" == Debra S Baddorf  writes:

DSB> Well, if it’s already not doing what you want, you might read
DSB> these.

Well, yeah, that's pretty much the same as I indicated that I'm using
now, except that I'm using different thresholds.  My problem is that I
asked for at least 70% usage and it's giving me just about 50%.  I also
checked the logs and it seems that it basically flushes every other day,
which is consistent with it always flushing existing dumps to tape at
startup.  So I'll turn off autoflush and see if that makes any
difference.

 - J<

Re: Always fill every tape

[Debra S Baddorf]

> On Mar 9, 2018, at 1:43 PM, Jason L Tibbitts III  wrote:
> 
> With tape sizes what they are now I'm finally at the point where I have
> way more tape than stuff to back up.  To satisfy my inherent laziness,
> I'd like to actually fill every tape (or at least come close to filling
> them).  And then just leave my library full of tapes without ever
> needing to change them out.
> 
> My understanding is that Amanda has no way to append to tapes; once it
> has started writing to a tape, that tape won't be used again until the
> next pass through the tapecycle.  That implies that you must keep
> backups on the holding disk and write them only when you'll have a
> nearly-full tape.  I have plenty of holding disk (at least until I move
> to LTO8) so that isn't an issue.
> 
> Currently I have these in amanda.conf:
> 
> tapecycle 47 tapes
> autoflush yes
> taperflush 70
> flush-threshold-dumped 70
> flush-threshold-scheduled 90
> 
> Is that basically all I'm supposed to do?  Because according to the
> reports, each tape is only getting about 50% full.  So I think I must be
> missing something about how those four flush-related parameters
> interact.
> 
> - J<

Well, if it’s already not doing what you want,  you might read these.  They’re 
from an
example  amanda.conf,   but I don’t know how current my copy is.

# You don't want to use a new tape for every run, but want to start writing
# to tape as soon as possible:
# flush-threshold-dumped0   # (or more)
# flush-threshold-scheduled 100 # (or more)
# taperflush100
# autoflush yes
# maxdumpsize   100k # amount of data to dump each run; see above.
#
# You want to keep the most recent dumps on holding disk, for faster recovery.
# Older dumps will be rotated to tape during each run.
# flush-threshold-dumped300 # (or more)
# flush-threshold-scheduled 300 # (or more)
# taperflush300
# autoflush yes

Deb Baddorf