Bryn Hughes wrote (2015/05/19):
> Yes, there is definitely a minimum throughput for LTO drives.  If you 
> aren't writing from local storage then you almost certainly won't be 
> able to meet it for anything at all modern.  LTO-3 was the last 
> generation that could be fed by a gigabit ethernet link (full speed is 
> 80MB/sec), newer technologies have much higher throughput rates.  As 

Even LTO-3 could be a problem to fully (= all the time) feed over gigabit
(using drive compression), but for all existing LTO-[123456] generations,
1 Gb/s is usually sufficient. When there is slower data stream, LTO tape
drive slows down physical tape movement speed. However, there are lower
limits already mentioned (~ 50 MB/s). There is often bigger problem in
many small files in source filesystem and native user/system disk load.

> When using spooling you give Bacula some space, it writes till it hits 
> whatever your max spool size is, then it stops spooling and writes out 
> that data to tape, when done it erases what it had on disk previously 
> and continues spooling data from where it left off. As mentioned above 
> there is an impact on your overall backup times with this as no new data 
> will be flowing in during the periods when Bacula is writing to tape, 
> however it'll keep your tape throughput in the 'happy' zone.

However when spooling job is finished, tape write is started immediately
and other spooling jobs do continue. So the second possibility is that
spooling never stops. In real scenarios, there is something between
these two cases.

-- 
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66  Brno, Czech Republic

------------------------------------------------------------------------------
One dashboard for servers and applications across Physical-Virtual-Cloud 
Widest out-of-the-box monitoring support with 50+ applications
Performance metrics, stats and reports that give you Actionable Insights
Deep dive visibility with transaction tracing using APM Insight.
http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users