Hi, at the moment I only backup to tape (LTO-3/4), but soon I'll start to do incremental and differential backups to disk. The gzip compression can only be enabled on a per job basis, thus it will be enabled for full backups to tape too.
The manual states that 'it is not generally a good idea to do both software and hardware compression'. I found similar opinions in the list archive. http://en.wikipedia.org/wiki/Linear_Tape-Open | LTO-DC | | The LTO specification describes a Data Compression method LTO-DC, also | called Streaming Lossless Data Compression (SLDC)[10]. [...] | The primary difference between ALDC and SLDC is that SLDC does not | apply the compression algorithm to uncompressible data (i.e. data that | is already compressed or sufficiently random to defeat the compression | algorithm). More specifically, for each block of data that the | algorithm works on, it saves a copy of the raw data and compares it to | the "compressed" data. If the "compressed" data is larger than the raw | data, it marks that block as raw and only saves the raw data to tape. | [...] | It should be noted that plain text, raw images, and database files | (TXT, ASCII, BMP, DBF, etc.) typically compress much better than other | types of data stored on computer systems. In contrast, encrypted data | and pre-compressed data (PGP, ZIP, JPEG, MPEG, MP3, etc.) would | normally increase in size if data compression was applied. This | expansion on tape is avoided by the SLDC algorithm. So with LTO it seems to be no problem to use gzip and the drives hardware compression. Any thoughts on this? Ralf PS: I would really love to see compression implemented in the storage daemon too. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
