Frank Smith wrote:
How difficult would it be to implement a 'best fit' strategy?
The number of possibilities is extremely large, and
because the tapecapacity is only an approximation, not worth
the cost. My AIT-1 tapes hit end of tape between 33 and 34 Gbyte.
And rarely there is one which suddenly hits EOT at 31.8 too.
One that would collect all the dumps to holdingdisk and then
fit them onto the tapes, the functional equivalent of running
amdump without a tape and then running amflush. I realize
that it would require holdingdisk size to be greater than the
total size of the backup, but it would allow for the most
efficient use of tape.
The "largestfit" performs very well on my setup: 3 of my 4
AIT-1 tapes are filled to nearly 100% on my archive run.
Last week one tape had even 100.6%.
Also, does Amanda always try to write another dump image
to tape until it hits EOT, even if the size of the dump is
greater than the amount of remaining tape?
For people that use hardware compression, amanda does not know
what remains on the tape. And even in my config, I had to
specify the tapelength a little pessimistic, because not all
tapes have equal capacity. The capacity of a tape is also
affected by the status of the write head and tape quality:
the drive reads with one head what it just wrote, and, if it
concludes that the written part is not good enough, the tapedrive
writes the same block again, up to a number of times (much faster
than stopping, rewinding and rewriting); this uses tapecapacity
too. That's why my tapelengths are less than the real length.
An improvement could be that, when nothing fits, amanda chooses
the smallest, which has the best chance of fitting on the uncertain
remaining inches (which in my case can be 1 Gbyte!).
--
Paul Bijnens, Xplanation Tel +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM Fax +32 16 397.512
http://www.xplanation.com/ email: Paul.Bijnens AT xplanation DOT com
***********************************************************************
* I think I've got the hang of it now: exit, ^D, ^C, ^\, ^Z, ^Q, F6, *
* quit, ZZ, :q, :q!, M-Z, ^X^C, logoff, logout, close, bye, /bye, *
* stop, end, F3, ~., ^]c, +++ ATH, disconnect, halt, abort, hangup, *
* PF4, F20, ^X^X, :D::D, KJOB, F14-f-e, F8-e, kill -1 $$, shutdown, *
* kill -9 1, Alt-F4, Ctrl-Alt-Del, AltGr-NumLock, Stop-A, ... *
* ... "Are you sure?" ... YES ... Phew ... I'm out *
***********************************************************************
|
