gary artim wrote:
> Hi --
> 
> Getting about 41.6/MBs and hoping for closer to the max (120MB). I
> tried maximum file sizes of 5, 8, 12GB -- 12GB the best the others
> where about 35/MBs. Any advise welcomed...should I look at max/min
> block sizes?

Don't adjust min size.

Bacula's max block size is ~2Mb (default 65535 bytes) and setting this 
should give a substantial speed boost (it did for me). Going higher than 
bacula's maximum will result in it failing throught to default, so 
double check the block size on a newly labelled tape before committing 
to any value.

WARNING: If you adjust this value, mark all current tapes as USED before 
restarting bacula-sd. Changing block size on an open tape is likely to 
lead to problems getting data off it.

LTO drives tend to have 16Mb maximum buffers. Perhaps Bacula's max block 
size needs increasing? (Kern?)

You should also enable spooling to _very_ fast disk before hitting the 
tape. LTO3 upwards will easily run faster than any spinning media and 
trivially outrun even a raid array if that has to do any seeking.

I use a raid0 set of 5 of Intel E25 60Gb drives and have seen 
throughputs approaching 700Mb/s out to 3 tape drives whilst other jobs 
are spooling (I've got 7 LTO5 drives carrying 6 pools but have never 
seen more than 3 writing simultaneously). These days I'd be more 
inclined to use one of the PCIe SSD cards as they're even faster, with 
less overhead.

> Device {
>   Name = LTO-4
>   Media Type = LTO-4
>   Archive Device = /dev/nst0
>   AutomaticMount = yes;               # when device opened, read it
>   AlwaysOpen = yes;
>   RemovableMedia = yes;
>   RandomAccess = no;
>   Maximum File Size = 12GB

   Maximum Network Buffer Size = 65536
   Maximum block size = 2M

   Spool Directory = /var/bacula/spool/LTO4
   Maximum Spool Size     = 280G
   Maximum Job Spool Size = 150G

>   Autochanger = yes
>   Alert Command = "sh -c 'tapeinfo -f %c |grep TapeAlert|cat'"
>   Alert Command = "sh -c 'smartctl -H -l error %c'"
> }

Enlarging network buffers is possible but it must be be the same 
everywhere and should be thoroughly tested first as it can as easily 
cause complete breakage as speedups - especially if backups are taking 
place across a routed network instead of just on your LAN.


AB



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