Kern Sibbald schrieb: > > > > 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).
Yes, I haven't found any improvement with bs > 128K. > > 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. Well, the LTO-3 drive is connected to a different server/sd, but the hardware is almost identical (Xeon 3000, 4 GB RAM). The 20 GB file was backed up from a RAID device which is capable of 130 MB/s seq. reads (tiobench). But I found a thread somewhere that you have to use multiple streams to get max. speed with LTO-4. Although I don't understand why this should be necessary if the backup source is able to deliver 130 MB/s and dd is able to write to tape with 110MB/s. I won't complain at all that ~80 MB/s is slow, just wondering where I could tune the system or bacula to get somewhere near 100-120 MB/s which LTO-4 (in theory) should be able to write to tape. Note: my backup over GbE was nearly as fast as the backup from disk on the local sd (~77 MB/s). If you have to backup multiple TB, every single MB/s counts ;) Ralf ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/bacula-devel
