[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Bacula-devel] MaximumBlockSize Problem and Question


On Thu, 2008-11-06 at 22:20 +0100, Kern Sibbald wrote:
> On Thursday 06 November 2008 22:02:26 Alex Chekholko wrote:
> > On Wed, 5 Nov 2008 16:12:51 +0100
> >
> > Kern Sibbald <kern@xxxxxxxxxxx> wrote:
> > > For writing to tape (providing it is LTO-n) I strongly recommend a block
> > > size not to exceed 256K.
> >
> > Hi Kern,
> >
> > Why do you say that?  
> 
> It is my experience with my own testing, and I asked the Quantum technical 
> gurus about using large blocks. They think it is not a good idea at all using 
> values larger than 512K and prefer as I do values around 256K.  The bigger it 
> is the more likely the tape writing will get out of phase and IMO the gain is 
> not worth the possible problems.
> 
> 
> > Is this thread relevant?: 
> > http://www.mail-archive.com/bacula-devel@xxxxxxxxxxxxxxxxxxxxx/msg01246.htm
> >l
> 
> Possibly.
> 
> >
> > Also, I would like to corroborate the OP's experiences; I had an almost
> > identical thread about small block size and slow write speed:
> > http://www.nabble.com/LTO-4-performance--td17407840.html
> >
> > In fact, I was unable to get higher block sizes working at all with
> > btape:
> > http://www.adsm.org/lists/html/Bacula-users/2008-05/msg00504.html
> >
> > So I am still stuck at ~22MB/s writing to LTO-4 with the default block
> > size.
> 
> There are a lot of other parameters to consider, but I cannot give such advice 
> any more -- no time:
> 
> - Up the block size to 128K or 256K and verify that it is being written that 
> size.

Hi,

Be warned!  Changing this parameter will deny access to existing
backup data.


>
> - Increase the Maximum File Size to about 5GB.
>

Are existing data still accessible when increasing
Maximum File Size ?  i hope so

BR
Ulrich

> - Use only *very* fast RAID disks running at 15,000 rpm.  Maybe soon we can 
> use SSD. 
> 
> - Get only the best disk and tape controllers.
> 
> - Get good quality, big, fast hardware -- you need hardware experts to get 
> lots of speed.
> 
> Then you need to do the same kinds of tuning of your network.
> 
> Regards,
> 
> Kern
> 
> 
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> Bacula-devel mailing list
> Bacula-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.sourceforge.net/lists/listinfo/bacula-devel

-- 
Ulrich Leodolter <ulrich.leodolter@xxxxxxxx>
OBVSG


-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Bacula-devel mailing list
Bacula-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/bacula-devel


This mailing list archive is a service of Copilot Consulting.