I've been reading through some of the articles about settings for my HP
LTO-5 drive. I have a question concerning FIXED vs VARIABLE block size.
1. Is it safe (Bacula 7.XX) to set the block size to something other
than 64K?
2. Does increasing the block size increase the throughput? (2 x 3.6Ghz
PROCS - 24 cores, 32GB RAM, 6x600GB 15K RPM SAS, external SAS / HP LTO-5)
3. Are there any down sides to increasing the block size? (e.g.,
existing tapes created)
SD configuration looks like:
Device {
Name = LTO-5
Media Type = LTO-5
Archive Device = /dev/nst0
AutomaticMount = Yes
AlwaysOpen = Yes
RemovableMedia = Yes
RandomAccess = No
AutoChanger = No
Maximum Spool Size = 500G
Maximum Job Spool Size = 100G
Maximum Concurrent Jobs = 5
Spool Directory = /var/spool/bacula
}
Despooling speeds avg 60+ MB/s. I also have a quad nic bonded
(bond-mode 6 with MTU 9000). I did run the btape test and speed. It's
results were much faster.
block size = 64K
btape -c /etc/bacula/bacula-sd.conf /dev/nst0
speed file_size=5 nb_file=8
Zero data / Raw Avg: 280 MB/s
Random data / Raw Avg: 111 MB/s
Zero / bacula Avg: 168 MB/s
Random / bacula Avg: 108 MB/s
O/S: Ubuntu 17.04 (so we could get a later version of bacula without
compiling from source)
I'm not overly concerned about the speed (everything backs up over night
fine) but I was hoping to get over 100 MB/s seeing that the LTO-5
theoretically can go up to 144 MB/s.
Any tips would be greatly appreciated.
Steven Hammond
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