On 6/4/2012 5:32 PM, Phil Stracchino wrote:
> I suspect that using SSD for data spooling would make little 
> difference to overall backup times unless the clients being backed up 
> could send data much faster than the storage server could spool it 
> without SSDs. It would probably be a larger performance gain if 
> simultaneous spooling and despooling were possible. My experience is 
> that spooling allows my LTo4 drive to spend more of its time running 
> at full speed, but lengthens my backup times significantly because 
> Bacula cannot continue spooling to a second file while a first is 
> despooled. I tried out spooling, but quickly disabled it as I found it 
> was hurting my backup performance overall, and my main NAS server has 
> enough data throughput to keep the LTO4 streaming almost continuously 
> anyway. What I do notice is that Bacula sits for some time - many 
> minutes - after each job ends doing nothing but batch-writing 
> attributes into the DB. 

I found that with SSD for MySQL, turning off attribute spooling 
altogether prevented that. Most of my clients machines are slow, so I 
notice no performance hit when not spooling attributes. With a lot of 
fast clients, it is possible that wouldn't be the case, but I suspect 
that, in general, using SSD for database storage negates the need for 
spooling attributes.

The nice thing about SSD is that "seek" delays are far shorter than with 
mechanical drives. I suspect the reason for the problem with writing a 
second spool file while reading the first is head seeks. Performing a 
sequential write in parallel with a sequential read is something that 
SSD is much, much better at than a mechanical drive, or even a RAID 
array of mechanical drives, simply because there are no heads to move.


------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users