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Re: [Bacula-devel] MaximumBlockSize Problem and Question


For writing to tape (providing it is LTO-n) I strongly recommend a block size 
not to exceed 256K.

On Wednesday 05 November 2008 14:48:20 Ulrich Leodolter wrote:
> On Wed, 2008-11-05 at 13:34 +0200, Pasi Kärkkäinen wrote:
> > On Wed, Nov 05, 2008 at 11:12:01AM +0100, Ulrich Leodolter wrote:
> > > Hello,
> > >
> > > Problem:
> > >
> > > Settings like (documented in the Manual)
> > >
> > >      Minimum block size = 64K
> > >      Maximum block size = 200K
> > >
> > > do not work. Both are defined as size_pint32.
> > > multipliers like K M are not allowed.
> > > don't know if this is intended,
> > > maybe documentation just a little outdated.
> > >
> > >
> > > Question:
> > >
> > > Can i expect performance improvements (especially for
> > > Copy/Migrate Disk to Tape jobs) by by increasing
> > > "Maximum block size" on File devices in bacula-sd.conf ???
> > >
> > > Device {
> > >   Name = FileStorage
> > >   Media Type = File
> > >   Archive Device = /disk0/bacula/files
> > >   LabelMedia = yes;
> > >   Random Access = Yes;
> > >   Requires Mount = No;
> > >   AutomaticMount = yes;
> > >   RemovableMedia = no;
> > >   AlwaysOpen = no;
> > >   MaximumBlockSize = 1048576;         # 1M
> > > }
> >
> > I think it should make difference at least with tape drives..
> >
> > You can measure the difference with dd:
> >
> > dd if=/dev/null of=/dev/tape bs=<try_different_block_sizes_here>
> >
> > 4k, 64k, 256k, 1MB, 4MB etc.
>
> Hello,
>
> I dont think raw performance is bad, as u can see below
> (exeption is 4k block size on tape,
>  hopfully bacula does not use it :-)
>
> Maybe i should set
>
> 	Minimum Block Size = 4194304
>
> on both devices (Tape, File)
> This should reduce the number of block read/writes communication
> by a factor of 64.
>
> Will try it tonight,  unless u give me a very good hint how to
> optimize ;-)
>
> BR
> Ulrich
>
> ---++ Raw Tape Performance
>
> [root@troll ~]# dd if=/dev/zero of=/dev/nst1 bs=4k count=256k
> 262144+0 records in
> 262144+0 records out
> 1073741824 bytes (1.1 GB) copied, 48.2057 seconds, 22.3 MB/s
>
> [root@troll ~]# dd if=/dev/zero of=/dev/nst1 bs=64k count=64k
> 65536+0 records in
> 65536+0 records out
> 4294967296 bytes (4.3 GB) copied, 41.4204 seconds, 104 MB/s
>
> [root@troll ~]# dd if=/dev/zero of=/dev/nst1 bs=256k count=16k
> 16384+0 records in
> 16384+0 records out
> 4294967296 bytes (4.3 GB) copied, 34.1308 seconds, 126 MB/s
>
> [root@troll ~]# dd if=/dev/zero of=/dev/nst1 bs=1024k count=4k
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes (4.3 GB) copied, 32.3195 seconds, 133 MB
>
> [root@troll ~]# dd if=/dev/zero of=/dev/nst1 bs=4096k count=4k
> 4096+0 records in
> 4096+0 records out
> 17179869184 bytes (17 GB) copied, 119.205 seconds, 144 MB/s
>
> ---++ Raw SATA Raid Performance
>
> [root@troll ~]# dd if=/dev/zero of=/disk0/test.img bs=4k count=4096k
> 4194304+0 records in
> 4194304+0 records out
> 17179869184 bytes (17 GB) copied, 83.0424 seconds, 207 MB/s
>
> [root@troll ~]# dd if=/dev/zero of=/disk0/test.img bs=64k count=256k
> 262144+0 records in
> 262144+0 records out
> 17179869184 bytes (17 GB) copied, 81.8973 seconds, 210 MB/s
>
> > -- Pasi



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