Hi,
I'm backuping about 1.2TB of data hosted on a RAID5 Xserve RAID
connected on an (old) Apple XServer G5.
This is mostly big graphic files.
The director and sd (version 2.4.2) are running on a debian linux
machine, and the Xserver runs only a file daemon (version 2.4.2).
Up to now, the backup was done on an LTO-2 autochanger (connected to the
linux server), with decent speed (ie backup time for 1TB was about 10h
at 25 MiB/s which seems to meet the specs of LTO-2).
Since we are scaling our backup infrastructure, I purchased arcvault 24
LTO-4 autochanger and tried to perform the same 1.2TB full backup. I
enabled a 10GB area spooling on a local software RAID0 (sharing the
system disk), because I heard that LTO-4 needs a sustained stream of
data above 40MiB/s to prevent tape shoe-shining.
Unfortunately the backup now takes ages (because of the spooling), and
the despooling is at most at 33-35MiB/s (the server is also running
other applications).
26-Sep 09:17 backup-sd JobId 1944: Despooling elapsed time = 00:05:23,
Transfer rate = 33.24 M bytes/second
I'm trying to speed up this backup, that is:
1) speed up the spooling:
The transfer between the macosx server and the linux server is at best
of 30 MiB/s because of the network. Even though, both host are using
bonded gigabit ethernet channels, they only use one slave at the time
(there is no round-robin mode in 802.3ad).
What can I do, to speed up this?
I thought about splitting the volume in 2 parts, and have to File
Daemons running on differents ip or ports (so that communication will be
split on the channels).
Is it a good idea?
2) speed up the despooling to tape
I already increased the "Maximum Block Size" to 2MiB and "Maximum
Network Buffer Size" to 65535 to try to achieve 2).
Sequencially reading from the despooling device (with dd) gives at most
45MiB/s ~ 50 MiB/s.
Sequencially writing to the tape device (with dd) gives about 50 MiB/s.
But with bacula, I don't see any despooling faster than 35 MiB/s.
Any idea on how I could enhance the despooling speed?
Thanks for any answers,
--
Brice Figureau <brice+bacula AT daysofwonder DOT com>
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