Keith Brautigam wrote (2006/02/16): > What actual speed are you getting now during the de-spooling process?
Typically 60 - 80 MB/s (note that file boundaries on tapes temporarily slows down the speed), however now my backup is idle, so I could not see it right now. > Also, how would you recommend measuring how fast you are writing to the > tape (I realize you're on FreeBSD not Linux)? I'm new to having such a > fast drive and am also interested in in creasing write performance. On FreeBSD, I do use personally modified iostat with possibility to print timestamps for long offline monitoring, or standard iostat 1 or iostat [2345] output for online monitoring. On Linux, maybe I would try to use iostat -m 5 for offline monitoring and iostat -m 1 or iostat -m [23] for online monitoring.. > How did you arrive at using hardware RAID and seven drives? Was that It was one of our free video servers at a time ;o) > convenient with your hardware, or did you first try a smaller number of > drives (like I have) and find they were not enough? Unfortunately I'm going in the reverse way - now I have to switch to another machine and I'm currently trying two-core 3.2 GHz with 2 GB RAM, one disk for MySQL and 2 or 3 disks for data spooling using software RAID0 (gstripe). Then I will see, if it is or is not similar to the current state. > How do you find/set the number of repositions? What other sorts of > tuning did you perform on the drive? Interesting performance logs from drives can be readed using LOG_SENSE or MODE_SENSE SCSI commands. SCSI command reference for IBM LTO drives can be downloaded freely from internet, but reference for HP LTO drives was very hard to get for me (is there anybody with access to this type of documentation? HP has several books to this topic and I'm happy that I have personal access to atleast part 3 with SCSI command reference). Other information can be readed directly from my scripts located in ftp://ftp.cz.FreeBSD.org/pub/FreeBSD-local/scsi. > So it sounds like I should be okay with an older Adaptec 160 MB/s card? Please no ;o) I'm still afraid, that I could not see any speed differences because of another problem and would be happy to see experiences from the others. Maybe the problem is in FreeBSD and Linux would perform better. The problem is that I never seen value over 100 MB/s from iostat 1 output for any data even with good compression ratio, which looks suspicious. I use two patches for FreeBSD kernel: - Standard FreeBSD allows just 128 KB max. physical request (disks and so on), so I increase it to 384 KB (which is twice the size of max. allowed physical request for my LSILogic 1030 Ultra4 320 MB/s. - Standard FreeBSD allows just 64 KB max. physical request for SCSI tapes, so I increase it to 192 KB, where ~ 196 KB/t seems to be limit of LSILogic adapter card (Adaptec allows bigger physical blocks, however again without performance differences for me :o/). However, if you switch to another hardware/software, you can make your data unreadable: I had an Adaptec with 256 KB/t and after switching to LSI 192 KB/t, I had to have Adaptec still available, so that I would be ready to read data written with 256 KB/t (all is meant SCSI physically - it is different thing from OS layer, which can break down bigger requests to the smaller ones). Regards. -- Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar Brno University of Technology, Faculty of Information Technology Bozetechova 2, 612 66 Brno, Czech Republic ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
