In a message dated: Wed, 11 Aug 2004 13:34:06 BST
Maccy said:
>I'm after some advice, as I haven't had any experience of setting up a
>backup system before.
I apologize for the delay in responding, I was on vacation when you
posted this and am now just catching up on my Amanda mail :)
>I recently acquired a Overland Powerloader with 17 slots and 1 LTO-2
>drive.
Ahh, nice set up, that's what I have and really like it. Mine has a
barcode reader in it too, though I've not spent the time to configure
that yet (it's on the "todo" list when I find some more 'round tuits' :)
>I want to backup ~3TB of data, and I'd like to do it incrementally
>throughout the working week and fully Friday thru Sunday.
Not overly complicated, just run 2 different configurations.
(I'm assuming that the Fri-Sun backups are meant for offsite storage ?)
>Ideally I'd like 3 cycles on the full dump and 2 cycles of tapes for
>the incremental. I have a total of 25 LTO-2 tapes at my disposal.
>
>How would I go about labelling the tapes? Is there anything else I need to
>look for?
As I said, I would use 2 different configurations, a 'daily' and a
'weekly' configuration. (this is exactly what I do, incidently).
Set up 'daily' such that it runs Mon-Thu nights, and 'weekly' Fri-Sun.
The big problem is going to be your full dumps. Do you really want
to run a full dump Fri, Sat, and Sun? Or do you just want to run a
single full dump of the data allowing it to run over those 3 days?
If the former, then I'd recommend that you allow for incrementals of
some file systems to be done on certain nights. The reason is, 3 TB
is a lot of time, and if you can't get it all done in one night, then
there's no way you'll be able to back it all up on each of 3 nights.
For the tape division between the 2 configs, that really depends upon
how many tapes a single night takes. LTO2 tapes hold about 400GB
(compressed). You mentioned 3TB to back up, so you're talking, for a
level 0 of everything, about 8 tapes. You can probably cut that in
half for the daily incremental runs, since a level 0 doesn't need to
be done of everything every night. You could, perhaps, cut that back
to 2 tapes if you have a rather high bumpsize.
You'll also probably want to slowly introduce different file systems
into the backup strategy at first in order to avoid requiring 8 or
more tapes to start with. In other words, say you have 10 file
systems which comprise that 3TB. If your disklist contains them all
that first night, amanda will want to perform a level 0 of all 10
that first night. Some will fail if you run out of room on the tape
since it can't fall back to incremental (since it doesn't have a
level 0 to base that incremental on!). Rather, pick 2 or 3 file
systems to backup the first night, then add a couple more the second
night. Since those backed up the first night now have a level 0
base, amanda can bump those to a level 1, thereby making room for
level 0s of the new file systems. Continue this until all of your
file systems are in the disk list and have been backed up.
Then you can start playing with the bumpsize to tweak when amanda
bumps different file systems to new levels in order to save room.
So, assuming your able to get your daily incrementals onto 2 tapes
per night, times 4 nights, that's 8 tapes per week. You wanted 2
cycles for the incremental runs, that would be 16 tapes. Add a few
for good measure (to guard agains sudden expansion, or a bad tape)
and you've got 18-20 tapes in your daily config. Since you stated
you were limited to 25 tapes, you might want to keep it on the low
side, like 17-18 tapes. Additionally, since it's a 17 slot carrier
that fits in there, you probably want to occupy 16 slots with tapes,
and keep a cleaning tape in the 17th slot. You can reserve slots 0-7
for the daily tapes and 8-16 for the weekly tapes.
Now for the 'full dump' configuration. If you've allocated 18 tapes
for the incrementals, that only leaves you with 7 tapes for the full
dump configuration, which is pretty tight. There's almost no way
you'll fit 3TB onto 7 tapes at 400GB each. Especially if that 300TB
number is only going to grow. And you certainly won't be able to run
with 3 sets of full backups that way. If you really need to do full
backups Fri-Sun of all file systems, I'd invest in more tapes.
However, another alternative is to run a weekend configuration which
allows for incrementals. Essentially, this is just like the daily
incremental configuration. At 2 tapes per day, times 3 days, that's
6 tapes. You've got 7, which will handle either a bad tape, or a
sudden increase in data set size. Of course, this doesn't allow for
maintaing 3 *sets* of weekend tapes, so you'll still need more tapes
(I'd say at least 14; ( (2 tapes * 3 days) + 1 extra) * 2 weeks )
Well, that's a start anyway, and should give you something to think
about. I hope it's helpful. Feel free to ask more questions (or
provide more information about what your intentions are :) and we'll
do the best we can to help you get going.
--
Seeya,
Paul
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