Hi, 16.02.2010 21:37, Edward M. Markowski wrote: > > I thought about this reciently, after I moved my spool dir to a 1.5 GB > ramdisk, I had been using 100GB of a mirrored pair of 500GB SATA drives > my throughtput to tape went up be a little over 10Mps. > > A few thoughts, see inline...... > > On Tue, 16 Feb 2010, Arno Lehmann wrote: > >> Hi, >> >> 16.02.2010 11:50, Daniel Kamm wrote: >>> That's maybe a stupid question, but I really wonder... >>> >>> Using Disk Spooling prior to write data to tape, heads in a sequential >>> write order: >>> a) write data from backup client to disk spool directory >>> b) write data from spool directory to tape >>> >>> Why are those tasks done sequentially? >> >> I know those three reasons: >> - simultaneously spooling and despooling increases the requirements of >> your spool space storage system even more > > agree, but space is cheep, even boatloads of RAM :-)
With RAM disk, you indeed get a fast file system. However, many users of Bacula will not be able to add (or willing to pay for) RAM to get a useful spool ramdisk. Thus the approach to use must work reasonably fast with hard disks - size is not so much the problem here, rather the IO load. And, when using a small number of disks, this is typically the bottle neck. > >> - it's never been implemented >> - it's probably harder to implement than it looks at first. > > One way to implements this is to have several smallish spool partitions > with the producer and consumer processes never using the same one at the > same time. For this to be most efficient the partitions would have to > be on different disks/busses/controllers. > > A better way in my opinion is to used a spool sized ring buffer in > memory rather then a disk based spool. The consumer would only start > after the producer had put a large set amount in it and continued until > drained the buffer. Sure... those approaches are not exactly new, and they don't sound too complicated. However, to discuss this, -users is not the best place. If you want to propose an implementation, you should do that on -devel - I'm sure Kern would like to see actual patches ;-) My understanding of the situation is that, once you want to actually implement simultaneous spooling and despooling in a way that integrates well with Bacula you find there's a lot more work to be done than you expect at the beginning... Cheers, Arno > >> >>> Let's say if the spool is reaching a waterlevel mark, the storage daemon >>> will start to write the spool data to tape _and_ at the same time the >>> backup client still sends data to the spool directory. Isn't that >>> possible? >> >> It's not possible now, but IIRC this has been discussed quite often, >> but, while many users thought it might be a nice feature, nobody >> started actually working on it. >> >> There's actually a feature request regarding that, though it isn't on >> the web site yet. It is, though still unnumbered, in the projects file >> of the git tree. >> >> Cheers, >> >> Arno >> >>> Cheerz, >>> - Dan >>> >>> ------------------------------------------------------------------------------ >>> >>> >>> SOLARIS 10 is the OS for Data Centers - provides features such as >>> DTrace, >>> Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW >>> http://p.sf.net/sfu/solaris-dev2dev >>> _______________________________________________ >>> Bacula-users mailing list >>> Bacula-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/bacula-users >>> >> >> -- >> Arno Lehmann >> IT-Service Lehmann >> Sandstr. 6, 49080 Osnabrück >> www.its-lehmann.de >> >> ------------------------------------------------------------------------------ >> >> >> SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, >> Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW >> http://p.sf.net/sfu/solaris-dev2dev >> _______________________________________________ >> Bacula-users mailing list >> Bacula-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/bacula-users >> >> >> >> >> > > !DSPAM:4b7b01f411881014520154! -- Arno Lehmann IT-Service Lehmann Sandstr. 6, 49080 Osnabrück www.its-lehmann.de ------------------------------------------------------------------------------ SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW http://p.sf.net/sfu/solaris-dev2dev _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
