On Wed, Jul 30, 2008 at 11:45 AM, Kern Sibbald <[EMAIL PROTECTED]> wrote: > Hello, > > On Tuesday 29 July 2008 15:22:03 T. Horsnell wrote: >> What: >> That Bacula be modified to enable the simultaneous use of multiple tape >> drives, either as a bunch of freestanding units or as multiple drives in >> an autochanger. >> >> Why: >> For me personally, this would permit faster simpler backup of a large >> single filesystem. I have a two-drive LTO4 tapechanger and at present, >> in order to utilise both drives at once, I have to create two jobs each >> of which backs up part of the filesystem. This is not optimal as the two >> subparts can change size radically, meaning that one drive may spend >> much of its time idle. I also have to split my tapes into two pools, one >> for each job. >> I have seen one other similar request to the users list recently, >> whereby a user had a bynch of freestanding drives which he wanted to >> preload with a set of tapes once a week, and then have Bacula >> automatically organise his backup over the tapes as it saw fit. >> This may make a cheap alternative to a tapechanger. >> >> A device pool maybe? > > Technically I don't know how to do this project. The SD has blocks of data > coming in from the FD, and sending those blocks to multiple drives would be > extremely difficult to track -- I am not even sure how. Currently, they are > either sequential (if spooling is on) or at least written in order to a > single drive, so it is very easy to track and find them for restores. > > In addition, I don't think it is possible for any existing network connection > to run fast enough to drive an LTO4 tape drive at full speed, so this project > seems to add a lot of complexity to Bacula to give no improvement in > performance. If I am wrong about the network connection and an LTO4, please > show me the math :-) > > For the moment I cannot accept the Feature Request. If you can give complete > details of a design for tracking the blocks written to multiple tapes and how > to send them back to the FD in the same order, and if you can show with a > simulation that we would actually gain something, then you can resubmit it, > and I will reconsider adding it to the projects. After than, either someone > must submit a patch or the Bacula users vote and it becomes a top rated > project, in which case one of the developers would surely work on it. > I totally agree that sending data blocks to more than 1 device at a time for a single job at this time will be a very difficult task but when I read this I see that there are two basic feature requests and the second is not so bad. The second is to be able to continue a job on a different tape than the job started on. I can see this is useful if you have more than 1 drive of the same type.
John ------------------------------------------------------------------------- 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-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/bacula-devel
