On Wednesday 03 February 2010 13:59:59 Pascal Vandeputte wrote: > Dear Bacula developers, > > A few years ago I deployed IBM Tivoli Storage Manager in the company I > worked for at the time. Since then I've never really encountered a > backup product that could match it in terms of speed or resource > utilization, which can be entirely attributed to the "progressive > incremental" backup strategy it uses. A file is never transferred over > the network twice, TSM always takes incremental backups and keeps track > of files it already has somewhere in its backup pool by using a > relational database (IBM DB2 since TSM version 6). For a longer > explanation, see > > https://agora.cs.illinois.edu/display/tsg/Progressive+Incremental+Backups+e >xplained > > Only new files are transferred to backup storage, files which have > disappeared from the host since the previous backup are marked inactive > and eventually purged from backup storage depending on the defined > retention policies. It backs up to disk at night for speed, and > transfers from disk to tape during working hours in a FIFO manner. This > way restores are often almost instantaneous because the recent backup > data is still on disk. Other daytime tape maintenance operations involve > the creation of an off-site copy of the primary storage pool tapes > (which are always on-line (!), your tape library must be large enough to > accomodate this), reclamation (freeing tapes with mostly expired data) > and collocation (moving data from a specific host on as least tapes as > possible). > > The system works really well. Unfortunately no other backup product that > I know of implements the same backup strategy. As a side effect, there > is no real competition in this space and the licensing costs of TSM > aren't pretty... My current employer isn't a TSM shop and as I'm not > exactly thrilled with our current backup solution, I'm looking at > affordable TSM alternatives but it appears that there just aren't any. > > I hoped that Bacula's new "basejob" deduplication feature would start > offering something in this direction (as files in a basejob are only > backed up once), but now that I've read a bit more about it, it doesn't > seem to do what I hoped for. :-( > > What could be the reason no other companies or open source projects go > in this direction? There are great open source databases, there are > great open source backup projects, but there are none which attempt to > forge these technologies into an "always incremental" backup product (or. > "enterprise class data management system" as some prefer to call it...).
Bacula has had "progressive incremental or always incremental" since the very beginning of the project. It is however, in my opinion, a feature that had certain disadvantages tjat TSM doesn't mention much until a two recent Bacula features called VirtualFull and Accourate We just do not advertise it as much as TSM does, but it is there. Do a full and then incrementals, and when Bacula does a restore, it reads and restores only the last incremental written for each file. The downside of this is that if you don't have a VirtualFull+Accurate, you may end up with missing files and/or a very large number of volumes needed to do a restore. Base Job deduplication is yet another feature (Bacula only as far as I can tell) that can drastically reduce the amount of data transferred for a backup -- particularly for a Full backup. Best regards, Kern > > Best regards, > > Pascal > > P.S. The following document is a great introduction to TSM concepts: > http://www.redbooks.ibm.com/redpapers/pdfs/redp0044.pdf ------------------------------------------------------------------------------ The Planet: dedicated and managed hosting, cloud storage, colocation Stay online with enterprise data centers and the best network in the business Choose flexible plans and management services without long-term contracts Personal 24x7 support from experience hosting pros just a phone call away. http://p.sf.net/sfu/theplanet-com _______________________________________________ Bacula-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/bacula-devel
