>I have always wondered .. why does amanda pipe ufsdump output to ufsrestore
>before sending it to the tape device?
It's collecting the index data.
The dump (or tar) output pipeline is rather complicated. The image data
goes back to sendbackup who in turn tee's it to the restore program
to gather the index information (if indexing is enabled) as well as
sending the raw data (possibly through a compression program) back on
the network to a dumper process on the server side. The restore program
also feeds its results back through sendbackup to be sent to the dumper
on a different socket (as I recall). So sendbackup is multiplexing five
data streams:
* reading the dump image coming in from the backup program
* writing the image out to the index (restore) process
* writing the image out the socket connected to dumper on the server
or to a compression program
* reading the output of the index process
* writing the index data to another socket back to dumper
>If I ufsdump direct to tape, eg.
>
>ufsdump 0f /dev/rmt/0n /
>
>I consistently achieve 3mb/second (Exabyte mammoth).
>
>If amanda is dumping direct to tape (file systems that are bigger than the
>holding disk), I'm lucky if i get 1mb/second.
>
>If it's going from the holding disk to tape, I get 3mb/second, as expected.
But you're comparing apples and oranges. As you've noted, going from
disk to tape on the same machine gets 3 MBytes/s whether you are using
ufsdump or Amanda is using taper to copy a holding disk image.
But that's not what happens when Amanda is dumping a client direct to
tape. The data has to go across the network (even if it's all on the
local machine it still goes through the kernel network stack). And,
probably even more important, Amanda does compression when dumping,
not when writing to tape.
So a dump to holding disk would be "slow" but the corresponding holding
disk to tape operation would be "fast". But a direct to tape backup
would pay the penalty and show the speed loss due to compression even
though the tape I/O portion is going as fast as it is given data.
You didn't mention what kind of dump rates Amanda reports. Those should
more or less match your direct to tape numbers for large enough images
to get a good sample and with similar clients.
Note that I'm not saying something isn't wrong in Amanda. Just that we
need to narrow down the list of culprits.
>g.
John R. Jackson, Technical Software Specialist, [EMAIL PROTECTED]
