Dear Christoph

Yes the interleaving of the concurrent jobs slows down the performance.

I use job migration for my full backups from disc to tape and the 
migration actually removes the interleaving and if the disc volume is 40 
GB and there is a small 1 GB full backup in the volume it takes about 40 
minutes - a 20 GB in the same volume also takes about 40 minutes. The 
tape unit max transfer rate is about 50 to 60 GB / hour almost matching 
the discs.

The great benefit is restores are quick - I leave incremental backups on 
disc. The discs are 1TB firewire 400.

Regards
Stephen Carr


Christoph Litauer wrote:
> Christoph Litauer schrieb:
>> Dear bacula users,
>>
>> I am running bacula 2.4.2 on a linux box. My backups are written to 
>> disk1, a raid that is able to read/write about 80MB/s.
>>
>> I just did a 'restore all' to another local connected disk (disk2) 
>> (80MB/s read/write). While the restore was running I watched the 
>> throughput using iostat. I saw disk1 was reading about 70-80 MB/s but 
>> disk2 was just writing with 5-6MB/s.
>> It seems as if bacula does not just read the essential data from the 
>> backup device, instead it reads nearly all backup data and then writes 
>> the data that should be restored?
>>
>> My disk device is configured
>>
>> #
>> # File Storage
>> #
>> Device {
>>    Name = FileStorage
>>    Device Type = File
>>    Media Type = File
>>    Archive Device = /storage
>>    LabelMedia = yes;
>>    Random Access = Yes;
>>    AutomaticMount = yes;
>>    RemovableMedia = no;
>>    AlwaysOpen = no;
>>    Block Positioning = yes;
>>    Maximum Volume Size = 10737418240     # 10GB
>> }
>>
>> I think a restore rate of 5-6MB/s is rather slow and I'm shure bacula 
>> could do better. Any configuration mistake?
>>
> 
> Ok, I'll try an answer myself: As far as I read the documentation the 
> performance gap between reading and writing results from bacula not 
> storing the exact position for each file. Instead just the job position 
> is stored in the database so that restore jobs have to read the whole 
> job data.
> 
> As a conclusion: As far as I understand this fact, interleaving 
> (concurrent writing of up to 20 clients) causes significant performance 
> slowdowns while restoring? And would spooling help? Does spooling 
> unscramble the interleaved data?
> 

-- 
Stephen Carr
Computing Officer
School of Civil and Environmental Engineering
The University of Adelaide
Tel +618-8303-4313
Fax +618-8303-4359
Email sgcarr AT civeng.adelaide.edu DOT au

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