On Friday 05 October 2007 11:31, Ralf Gross wrote: > Ralf Gross schrieb: > > Chris Howells schrieb: > > > > After spooling bacula is writing to LTO with 70Mb/s here. > > > > > > > > 02-Sep 06:47 VU0EM005-sd: Despooling elapsed time = 01:43:59, > > > > Transfer rate = 72.28 M bytes/second > > > > > > > > This is with the default block size and only one single job. > > > > > > Is that LTO 4? What model tape drive? > > > > It's an IBM Ultrium-TD3 drive (LTO-3, sorry for skipping that info), > > NEC-T40A 40x changer. > > > > > That's bizarre. What HBA are you using? Would also be interesting to > > > know what OS. I've got a Symbios Logic SAS1068 PCI-X Fusion-MPT SAS on > > > Ubuntu 6.10. Kernel 2.6.15, which I guess is rather old now. > > > > SCSI storage controller: Adaptec AIC-7901 U320 (rev 10) > > Debian Etch/4.0 amd64 > > > > The transferrate depends on the type of backup and if spooling was > > used. > > Update: > > With dd and different block sizes I get 100-115 MB/s (bs=64k to > 256k). This was only a simple test with the new LTO-4 drive. Changing > the bs to more than 128 didn't result in better performance. > > A simple test with tar was much slower (~60 MB/s, didn't touch the > bs). > > I didn't test bacula with other bs than the default, but I get ~77 > MB/s for a backup of a file on the sd (fd/sd on the same server) where > the LTO-4 drive is connected to (Attribute Spooling enabled, just one > 20 GB file).
This seems to confirm what I have been saying that the 64K block size is not so bad (128K may be better for an LTO-4), and increasing the block size to many megabytes as proposed by some people probably won't improve performance (and IMO may increase tape errors). > > I'm not sure why backup to LTO-4 isn't faster than the backup to > LTO-4, but the result is not that bad. I assume you meant the second LTO-4 to be LTO-3. The answer to your question is that you are probably talking about different systems, so they are almost impossible to compare, and even if you are talking about the same system, as I understand you need RAID disks to be able to drive an LTO-4 at full speed, or multiple disks and multiple simultaneous jobs. From what I understand maximum LTO-4 transfer speeds are significantly faster than most disk speeds. Thanks for the info ... Kern ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Bacula-devel mailing list Bacula-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-devel
