On Thursday 06 November 2008 22:02:26 Alex Chekholko wrote: > On Wed, 5 Nov 2008 16:12:51 +0100 > > Kern Sibbald <[EMAIL PROTECTED]> 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/[EMAIL PROTECTED]/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. - Increase the Maximum File Size to about 5GB. - 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-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
