Re: [Bacula-users] LTO3 tape capacity lower than expected

Thomas Mueller wrote:
>>> maybe this is the reason for the "extra mb/s".
>> Modifying the Maximum Block Size to more than 262144 didn't change much
>> here. But changing the File Size did. Much.
> 
> I found a post from Kern saying that Quantum told him, that about 262144 
> is the best blocksize - increasing it would increase error rate too. 
> 
>> Anyway, 40 MB/s seems a bit low, even with the defaults. Before tuning
>> our setup I got ~75 MB/s. Are you spooling the data to disk or writing
>> directly to tape?
> 
> yes, i was surprised too that it is that slow. 
> 
> I'm spooling to disk first (2x 1TB disk as RAID0, dedicated to bacula for 
> spooling). i will also start a sequential read test to check if the disks 
> are the bottleneck. The slow job was the only one running.
> 
> watching iotop i saw the "maximum file size" problem: it stops writing 
> after 1 GB (default file size) and writes to the DB and then continues 
> writing. so for a LTO-4 it stops nearly 800 times until the tape is full. 

I've also increased the Maximum File Size, I'm spooling of a ram-disk to
LTO4 tapes seeing rates like this:
04-Jan 23:09 bacula-sd JobId 33739: Despooling elapsed time = 00:01:22,
Transfer rate = 121.9 M bytes/second
04-Jan 23:15 bacula-sd JobId 33739: Despooling elapsed time = 00:01:24,
Transfer rate = 119.0 M bytes/second
04-Jan 23:21 bacula-sd JobId 33739: Despooling elapsed time = 00:01:24,
Transfer rate = 119.0 M bytes/second
04-Jan 23:26 bacula-sd JobId 33739: Despooling elapsed time = 00:01:21,
Transfer rate = 123.4 M bytes/second
04-Jan 23:31 bacula-sd JobId 33739: Despooling elapsed time = 00:01:25,
Transfer rate = 117.6 M bytes/second
04-Jan 23:40 bacula-sd JobId 33734: Despooling elapsed time = 00:01:06,
Transfer rate = 151.5 M bytes/second
04-Jan 23:46 bacula-sd JobId 33734: Despooling elapsed time = 00:00:56,
Transfer rate = 178.5 M bytes/second
04-Jan 23:53 bacula-sd JobId 33734: Despooling elapsed time = 00:01:00,
Transfer rate = 166.6 M bytes/second
04-Jan 23:57 bacula-sd JobId 33734: Despooling elapsed time = 00:00:57,
Transfer rate = 175.4 M bytes/second
05-Jan 00:02 bacula-sd JobId 33734: Despooling elapsed time = 00:01:02,
Transfer rate = 161.2 M bytes/second
05-Jan 00:08 bacula-sd JobId 33734: Despooling elapsed time = 00:01:00,
Transfer rate = 166.6 M bytes/second
05-Jan 00:12 bacula-sd JobId 33734: Despooling elapsed time = 00:00:52,
Transfer rate = 192.3 M bytes/second
05-Jan 00:17 bacula-sd JobId 33734: Despooling elapsed time = 00:00:59,
Transfer rate = 169.4 M bytes/second
05-Jan 00:22 bacula-sd JobId 33734: Despooling elapsed time = 00:00:58,
Transfer rate = 172.4 M bytes/second
05-Jan 00:29 bacula-sd JobId 33734: Despooling elapsed time = 00:00:58,
Transfer rate = 172.4 M bytes/second
05-Jan 00:37 bacula-sd JobId 33734: Despooling elapsed time = 00:00:58,
Transfer rate = 172.4 M bytes/second

On LTO3 tapes in the LTO4 drive it tops at around 120MB/s.

-- 
Jesper

------------------------------------------------------------------------------
This SF.Net email is sponsored by the Verizon Developer Community
Take advantage of Verizon's best-in-class app development support
A streamlined, 14 day to market process makes app distribution fast and easy
Join now and get one step closer to millions of Verizon customers
http://p.sf.net/sfu/verizon-dev2dev 
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users