Eric, Kern, Thanks a lot for your concise and clear answers! I'm really itching to thoroughly start testing Bacula now.
If it works as well as you describe, and I expect it will, I honestly believe those VirtualFull + Accurate features should be advertised a lot more. Seriously :-) Thank you for your time, Pascal On 02/03/2010 02:58 PM, Kern Sibbald wrote: > 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 >> > > >
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