On Thursday 23 September 2004 12:02, Ivan Petrovich wrote:
>Gene,
>
>> While I'm not familiar with your setup Ivan, an 8 hour runtime
>> would seem to indicate configuration problems, like doing all
>> compression on the server rather than offloading it to the
>> clients, possibly a high rate of network errors due to bad cabling
>> or any combination of all the things that Murphy guy can dream up.
>
>The server and the client are on the same host. For one of my test
>sets, I was backing up NFS-mounted files to another NFS-mounted
>volumes as illustrated below.
>
>   [Host A, NFS server] -- Hard Drive X, Hard Drive Y
>
>   [Host B, NFS client, amanda server, amanda client]
>
>Here I used Host B to backup files on Hard Drive X to a set of
>"virtual tapes" on Hard Drive Y.
>
>I have another configuration which I have been running for 2-3 weeks
>now. This one does use real tapes, but it still gets its files via
> NFS.
>
>   [Host A, NFS server] -- Hard Drive X
>
>   [Host B, NFS client, amanda server, amanda client] -- Tape drive
>
>Here I use Host B to back up files on Hard Drive X to the tape
> drive.
>
>Yes, this is not the most optimum hardware configuration, but it is
>dictated by other operational constraints.
>
>Also, for this set, I have over 100GB of data, which works out to be
>about 30GB (both levels 0 and 1) spread out over a cycle of 4 days
> and 5 tapes. Each nightly run takes 4 hours--uncompressed.
>
I'm puzzled, 4 days, but 5 tapes?  Whats the 5th tape?

>I might try turning on software compression and see if, after one
>night of needing 8 hrs to run to gather the compression ratios, it
>will settle back to the 4 hr run time.

I suspect it will take more than 1 run to settle, generally the first 
dumpcycle is the settling base, and it fine tunes things from there 
on an every run basis.  I've seen it take 2 dumpcycles to get back to 
'routine' after making major changes in things.

>But at this point, I also don't have a real need for compression for
>the following reasons. Please tell me if you think any of them is
>silly.
>- I like the idea of a 1-week tape cycle, with only 4 runs and using
> 5 tapes each week. I don't wish to make the cycle any smaller
> because I like to have several days' worth of backup.

Bear in mind that a full backup isn't any one tape, but every tape for 
the most recent dumpcycle days will be required to do a full bare 
metal recovery.

>- With my amount of data (100+ GB), Amanda only fills each AIT-2
> 50GB tapes to about 60% capacity (~30GB).
>- Software/hardware compression will not reduce the number of tapes
>per cycle for as long as I choose to have a 4-run/5-tape cycle. It
>will only reduce the amount of data dumped onto each tape.
>- Had Amanda allowed us to append tapes, then I probably could have
>turned on compression, and expect to save 50% in tapes. But since
> each run needs to use one tape, whether it fills it 1% or 100%, I
> don't see any benefit in using compression.
>
>Any thoughts?

In your case, I cannot see any advantage to using compression, 
hardware or software.  Of course if the business grows, the database 
will eventually have to become compressed as it will outgrow both the 
backup medium and likely the rest of the hardware will need refreshed 
with faster stuff too at about that same time.

>Thanks.
>
>Ivan

-- 
Cheers, Gene
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