Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-15 Thread Alan Brown
On Sat, 13 Oct 2007, Ralf Gross wrote:

 FYI: the HP Ultrium 1840 LTO-4 drives have a buffer size of 128MB.

Are these FC or LVD interface?

AB


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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-15 Thread Ralf Gross
Alan Brown schrieb:
 On Sat, 13 Oct 2007, Ralf Gross wrote:
 
  FYI: the HP Ultrium 1840 LTO-4 drives have a buffer size of 128MB.
 
 Are these FC or LVD interface?

We have two drives with LVD interface.

http://h18006.www1.hp.com/products/storageworks/ultrium1840/specs.html

Ralf

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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-15 Thread Alan Brown
On Mon, 15 Oct 2007, Ralf Gross wrote:

 Are these FC or LVD interface?

 We have two drives with LVD interface.

 http://h18006.www1.hp.com/products/storageworks/ultrium1840/specs.html

Ah, standalone drives.

I was doubtful that the FC-LVD routers in MSL-series changers could keep 
up with LTO4



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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-15 Thread Ralf Gross
Alan Brown schrieb:
 On Mon, 15 Oct 2007, Ralf Gross wrote:
 
  Are these FC or LVD interface?
 
  We have two drives with LVD interface.
 
  http://h18006.www1.hp.com/products/storageworks/ultrium1840/specs.html
 
 Ah, standalone drives.

Well, the two drive are in a Overland Neo 4100 changer.
 
 I was doubtful that the FC-LVD routers in MSL-series changers could keep 
 up with LTO4

I've only limited experience with FC and haven't used it with tape
drive.

Ralf

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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-13 Thread Ralf Gross
Alan Brown schrieb:
  Also, as I said, I remain very skeptical about sizes greater than 500K, and
  there is even a certain amount of evidence from my own tests and from 
  several
  other users that increasing the size above 128K makes no significant
  difference.
 
 FWIW the tape drives I'm using (HP LTO2 drives in a 60 slot robot) appear 
 to have 2Mb internal buffering. You may well be correct as long as the SD 
 can feed data to the drives fast enough to keep up, but even a SAN fabric 
 can become congested at times.

FYI: the HP Ultrium 1840 LTO-4 drives have a buffer size of 128MB.

Ralf

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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-12 Thread Alan Brown
On Fri, 12 Oct 2007, Kern Sibbald wrote:

 And I did as I said I will increase this limit,.

OK, I missed that bit/

 Also, as I said, I remain very skeptical about sizes greater than 500K, and
 there is even a certain amount of evidence from my own tests and from several
 other users that increasing the size above 128K makes no significant
 difference.

FWIW the tape drives I'm using (HP LTO2 drives in a 60 slot robot) appear 
to have 2Mb internal buffering. You may well be correct as long as the SD 
can feed data to the drives fast enough to keep up, but even a SAN fabric 
can become congested at times.

AB



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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-12 Thread Kern Sibbald
On Friday 12 October 2007 15:18, Alan Brown wrote:
 On Fri, 12 Oct 2007, Kern Sibbald wrote:
  And I did as I said I will increase this limit,.

 OK, I missed that bit/

  Also, as I said, I remain very skeptical about sizes greater than 500K,
  and there is even a certain amount of evidence from my own tests and from
  several other users that increasing the size above 128K makes no
  significant difference.

 FWIW the tape drives I'm using (HP LTO2 drives in a 60 slot robot) appear
 to have 2Mb internal buffering. You may well be correct as long as the SD
 can feed data to the drives fast enough to keep up, but even a SAN fabric
 can become congested at times.

I suspect that tape drive chop up blocks to suit their needs so that they can 
index for doing quick forward spacing.  From what I understand, older drives 
wrote in 512 byte chunks no matter what you did.  This is unlikely to be true 
for modern drives, but then modern drives probably buffer up a meg or so of 
data before writing it, so I suspect that the block size is pretty irrelevant 
after a certain point.  It all comes down to how fast Bacula can feed the 
data, and that is restricted either by the disk speed if you are spooling, or 
the comm line speed if you are writing directly.

I'm starting to get contacts in hardware manufacturing companies, so will 
bring up this issue with them at some appropriate point, so we can get the 
point of view of a manufacturer.

Regards,

Kern

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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-12 Thread Alan Brown
On Thu, 11 Oct 2007, Kern Sibbald wrote:

 Version 2.2.5 is a major bug fix release to version 2.2.4
 - It fixes the following bugs: #961, 962, 963, 969, 968, 960,
  964, (possibly 935 and 903), 953, 953, 967, 966, 965, 954,
  957, 908, 958, and 955.

Looking at this, it appears you simply closed 957

Given the _wide_ range of tape speeds now available, perhaps some way of 
dynamically changing the buffer sizes might be in order?

Failing that, the ability to test varying buffer sizes in btape and then 
allow user-selectable buffer size in SD?


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Re: [Bacula-users] Bacula 2.2.5 source + Win32 binaries released to Source Forge

2007-10-12 Thread Kern Sibbald
On Friday 12 October 2007 12:15, Alan Brown wrote:
 On Thu, 11 Oct 2007, Kern Sibbald wrote:
  Version 2.2.5 is a major bug fix release to version 2.2.4
  - It fixes the following bugs: #961, 962, 963, 969, 968, 960,
   964, (possibly 935 and 903), 953, 953, 967, 966, 965, 954,
   957, 908, 958, and 955.

 Looking at this, it appears you simply closed 957

I closed bug 957 with the following comment:

==
I think you are complaining about a problem that does not exist so I am 
closing this bug report. The current default is quite appropriate, anything 
larger would be inappropriate for a large class of drives that exist today.
 
 If you have a particularly fast drive, you *can* increase the Maximum Block 
Size. It is currently limited to 1MB, but you can modify the code if you 
want. I will increase this limit, but remain *very* skeptical about block 
sizes greater than 500K, and even that is quite large. For most tape drives 
(I don't know about LTO-4) 250K is probably more reasonable. 
===

And I did as I said I will increase this limit,.  Previously it was at 
100, in 2.2.5, it is set to 4096000.  Also the submitter was confused 
about how setting buffers in Bacula and tried to change the maximum buffer 
size by setting the minimum buffer size, and at some point (if I remember 
right) Bacula crashed or did something nasty.  I've added code in 2.2.5 to 
test for this inconsistent setting in the conf file and to immediately 
terminate with and appropriate error message.   

As a consequence, I don't think it is correct to say that I simply closed the 
bug report.

Also, as I said, I remain very skeptical about sizes greater than 500K, and 
there is even a certain amount of evidence from my own tests and from several 
other users that increasing the size above 128K makes no significant 
difference.  


 Given the _wide_ range of tape speeds now available, perhaps some way of
 dynamically changing the buffer sizes might be in order?

From day one you have had the ability to dynamically change buffer sizes and 
it works as long as you change the Maximum Buffer Size and not the Minimum 
Buffer size.  This maximum was previously restricted to 1MB, and now it is 
restricted to 4MB.  

As I wrote to the submitter -- I think you are complaining about a problem 
that does not exist.


 Failing that, the ability to test varying buffer sizes in btape and then
 allow user-selectable buffer size in SD?

From the beginning of Bacula you have had the ability to dynamically change 
buffer sizes both in btape for testing and in Bacula. 

I recommend against changing the buffer size, and have documented the 
consequences and how to work around them long ago in the manual.  You are 
free to change it, but you do so having been warned (i.e. at your own risk).

Regards,

Kern

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