Re: adding tapes to cycle
2009-05-06 14:43:36
Brandon Metcalf wrote:
----- Chris Hoogendyk <hoogendyk AT bio.umass DOT edu> wrote:
Chris Hoogendyk wrote:
Brandon Metcalf wrote:
I am currently using the following default settings:
dumpcycle 4 weeks
runspercycle 20
tapecycle 25 tapes
If wanted to, say, have an 8 week dumpcycle could I simply add and
label 25 tapes and change the parameters above to
dumpcycle 8 weeks
runspercycle 40
tapecycle 50 tapes
and expect Amanda to do the right thing?
Short answer: Yes. Of course.
A bit more: You can change your configuration and then feed it a few
more tapes at a time until you reach your full number of tapes. As
long as it has a new labeled tape each time it wants one, it will
continue to work. When you run out of new labeled tapes, then there
need to be enough tapes that there will be an old one that can be
re-used. Typically, you have a few more tapes than specified in
tapecycle. If runtapes is greater than 1, then you need more -- see:
http://wiki.zmanda.com/index.php/Tapecycle.
I want to amend my comments with one caveat.
While Amanda will do "the right thing," to some extent it will be
hamstrung by your configuration. You will typically only have one full
backup at a time (within a dumpcycle). You will have the constant threat
of having a full for some DLE overwritten, and the incrementals that
relate to that full becoming meaningless, before you have another full.
In addition, a single tape failure can result in multiple DLE's not
being recoverable.
If you changed your original scheme to
dumpcycle 2 weeks
runspercycle 10
tapecycle 25 tapes
Then you would always have a full backup, and often two.
If you add 25 tapes and make your new scheme
dumpcycle 4 weeks
runspercycle 20
tapecycle 50 tapes
Then, again, you will always have a full backup.
I don't know if your intention in stretching out the tapecycle is to
have more coverage, or whether you have too much data for your
network/server/tapes to handle in the shorter cycle. I would be
concerned about redundancy. If you aren't having trouble with too much
data, I would use a scheme like
dumpcycle 1 week
runspercycle 5
tapecycle 50 tapes
or, perhaps, 2, 10 and 50.
My motivation behind asking the question was to have more coverage. I
certainly don't have a problem with too much data as I'm using virtual tapes on
a large NAS RAID array. I was thinking that by increasing the number of tapes
and the dumpcycle and runspercycle parameters, I could recover further back in
time. It sounds like this may not be the case which is probably due to my lack
of understand of exactly how Amanda uses these parameters in its algorithms.
Assuming that I don't have a issue with too much data and I would like the
following to happen
* a full backup once per week
* backups 6 days per week
* the ability to go back a couple of months
Would a config like the following work?
dumpcycle 1 week
runspercycle 6
tapecycle 75
And could I simply add all of the virtual tapes and once and change the above
parameters and be OK?
Thanks for the help.
That would work.
You get at least one full backup of each DLE during each dumpcycle. On
other runs of amdump during the dumpcycle, it will do incrementals of
those DLE's. So every run you get a mix of fulls and incrementals, which
evens out the load.
A tapecycle of 50 (which you originally mentioned) would take you out to
8 weeks and a couple of days, given that you are doing 6 runs per week.
A tapecycle of 75 would take you out to 12 and a half weeks.
Watch your NAS carefully. In a sense, you are putting all your eggs in
one basket. If it is made up of consumer grade SATA disks, I would even
use raid 6 rather than raid 5, and I would still watch the logs
religiously to catch any signs of disk failures and swap them out promptly.
--
---------------
Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<hoogendyk AT bio.umass DOT edu>
---------------
Erdös 4
|
|
|