Hello,
On Thu, 2009-01-08 at 12:21 -0500, J-P wrote:
> Hi everyone,
>
> I wrote an e-mail regarding this issue before Christmas and had some good
> replies - Thanks to all. However, we were still unable to solve the issue.
> We decided to upgrade from 2.0.3 to 2.4.2 (using Ubuntu packages from
> Hardy-Backports) to see if we could get it solved.
>
> Unfortunately, it didn't solve the slow migration to tape issue. We had a
> suggestion from Ulrich to move spooling to another RAID array, which can't
> be done at the moment. So I'm looking at other solutions (if possible).
>
> Here is a recap of our situation:
>
> - Backups are taken from network clients to the Director/SD hard disk
> (RAID0, with MySQL on the same array) and then later migrated from disk to
> Tape (LTO3 with hardware compression)
> - When migrating, it takes hours to write some MB to the tape (i.e. 1h45mins
> for 5MB, with a rate of 0.9KB/s)
> - I tested the Tape drive with dd and have good throughput, around 135MB/s.
>
>
> Related to that, I have 2 questions:
>
>
> Question 1:
>
> When I do a migration to tape, while the first job is migrated, I'm
> executing "status storage=Tape" and I see something like the following
> output:
>
> --snip--
> Device status:
> Autochanger "Autochanger" with devices:
> "IBM-ULTRIUM-TD3" (/dev/nst0)
> Device "FileStorage" (/backup/bacula) is mounted with:
> Volume: WeeklyFileVolume-0002
> Pool: *unknown*
> Media type: File
> Total Bytes Read=159,528,829,516 Blocks Read=1,360,087
> Bytes/block=64,512
> Positioned at File=57 Block=2,323,636,495
> Device "IBM-ULTRIUM-TD3" (/dev/nst0) is mounted with:
> Volume: 000014L3
> Pool: Weekly Tape Pool
> Media type: LTO-3
> Slot 4 is loaded in drive 0.
> Total Bytes=87,741,932,544 Blocks=0 Bytes/block=64,512
> Positioned at File=0 Block=1
> --snip--
>
> >From "FileStorage", the "Total Bytes Read" always go over the "Total Bytes"
> in the "IBM-ULTRIUM-TD3" section. Why is that? Isn't supposed to be the same
> total in both section? It seems like the following is happening:
>
> 1. Read and write to tape (I've done the math, and write speed is around 3
> GB/min there?!)
> 2. When job writing is done, the FileStorage read continues (I think this is
> where we have a problem)
Bacula reads till the end of your FileStorage Volumes because BSR
matching doesn't work.
Without spooling relative small jobs are split into many smaller blocks
which are spread over your FileStorage volume (maybe uniformly
distributed, depends on client speed, number of backup jobs and
Maximum Concurrent Jobs). You can check this in the JobMedia sql table.
During migration Bacula seeks to the first block and then reads to the
end of the volume (because BSR matching doesnt work).
Bacula does NOT SEEK between consecutive blocks, it READS ALL BLOCKS
TILL THE END of the volume. This is done for each migration job.
(This is not 100% true, but almost)
> 3. When reading is done, "Migration OK" e-mail report is sent, showing poor
> stats about duration and speed rate.
>
> Can someone explain that to me?
>
>
> Question 2:
>
> Would spooling help in our situation? Or it is just a waste of Disk I/O
> since it is a migration from local hard disk to Tape Drive and not backup
> from a network client directly to Tape?
Spooling would definitely help, this was my experience.
But you have to limit the size of your FileStorage Volumes
to relative small size (depends on your average incr/full job size,
i used Maximum Volume Bytes = 4G).
This problem is fixed in the latest beta 2.5.28-b1,
but not in 2.4.x AFAIK.
Ulrich
PS: check
Device {
Name = "IBM-ULTRIUM-TD3"
...
AlwaysOpen = yes
}
>
>
> Thanks for you help, very appreciated!
>
>
> J-P
>
>
>
>
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