Yes, it seems that bacula 5.2.6 has a problem or is not accepting the change 
for larger Maximum Block Size:

------
Device status:
Device "FileStorage" (/tmp) is not open.
Device "LTO4" (/dev/nst0) is mounted with:
    Volume:      FA0060
    Pool:        BackupSetFA
    Media type:  LTO4
    Total Bytes=13,974,653,952 Blocks=216,620 Bytes/block=64,512
    Positioned at File=1 Block=50,181
====

It's falling through down to 64512 when I have anything set larger than 2097152 
for maximum block size.

WITH 2097152 as maximum block size I'm getting:

---
Device status:
Device "FileStorage" (/tmp) is not open.
Device "LTO4" (/dev/nst0) is mounted with:
    Volume:      FA0060
    Pool:        BackupSetFA
    Media type:  LTO4
    Total Bytes=223,244,193,792 Blocks=106,452 Bytes/block=2,097,134
    Positioned at File=20 Block=4,070
====
--

which is smaller than what I'm setting by ?18 bytes?  I don't get that at all.


Looks like there may also be a file system prefetch caching issue on top of 
this as even with the above larger block size I'm still only getting 50MB/s  
(this is now on a raid-0 of 16 2TB drives).


>From: Steven Ellis
>
>>On 4/12/2012 5:55 PM, Steve Costaras wrote:
>> My bacula-sd.conf is:
>>
>> ---
>> Device {
>>    Name = LTO4
>>    Changer Device = /dev/sg87
>>    Alert Command = "sh -c 'smartctl -H -l error %c'"
>>    AlwaysOpen = yes;
>>    Archive Device = /dev/nst0
>>    AutomaticMount = yes;
>>    Maximum Block Size = 4194304
>>    Maximum File Size = 10G
>>    Maximum Job Spool Size = 800G
>>    Maximum Network Buffer Size = 262144
>>    Maximum Spool Size = 12800G
>>    LabelMedia = No
>>    Media Type = LTO4
>>    RandomAccess = no;
>>    RemovableMedia = yes;
>>    Spool Directory = /scratchdir/spool0
>> }
>> -------
>That does seem to be what it indicates to me (but I'm still running 
>5.0.3, so YRMV), however, I found that my end-of-media messages 
>typically look like this:
>
>2012-03-04 11:30:20 sweety-sd End of Volume "MO0038L3" at 92:1171 on 
>device "LTO3" (/dev/nst0). Write of 262144 bytes got -1.
>2012-03-04 11:30:24 sweety-sd Re-read of last block succeeded.
>
>And my block size is set to 262144 (aka 256K), whereas the default block 
>size is 64512, (aka 63K)--since you are seeing a (presumably full, but 
>maybe not) block that fills the media being only 63K long, it at least 
>seems that somehow your configured block size is not being observed.
>
>Another point towards that end, even assuming that the current file on 
>the tape was nearly complete (i.e. 10GByte), then it isn't possible that 
>you were at block 91229 (which the log message indicates you were) with 
>a block size anywhere near 4MB (in fact, 10GiB/91229 = ~115KiB). It 
>looks like the largest possible average block size you saw in the last 
>file was about 115Kbytes (and if the last file was a bit less than half 
>complete, this would be consistent with an average block size of ~63K).  
>I don't fully understand bacula's blocking mechanism, but this seems 
>unusual to me (given your configured file size of 10G and maximum block 
>size of 4M).
>
>-se





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