Re: [Bacula-users] Compression Exb-8900
Quoting Trevor Morrison [EMAIL PROTECTED]: Hi, I have an Exabyte-8900 20/40 GB drive and it does a great job backing up my boxes. My question is: After about 25 GB, Bacula says the tape is full and wants another tape. According to the LCD display on the drive itself, compression is turned on. So, how can I tell Bacula to write up to 40 GB worth of data to the tape before changing? The 40GB is relatively unrealistic 1:2 compression. The real compression (and tape's capacity) that you'll get depends on the files you actually back up. If they were already compressed, you won't get any compression in the drive (you can't compress compressed files), so you'll fit only about 20GB worth of data on the drive (same as not using compression). If you are backing up text files (which can be nicely compressed) you'd be closer to 40GB. In general case, you could expect your compression ratio to be somewhere between 25% and 75%, but very rarely to be what manufacturer told you. Anyhow, if you have enough CPU power, I found that software compression (using gzip) does better job than hardware compression in the drive. If you are compressing files that can actually be compressed. See the compression option in the FileSet resource chapter. However, unlike hardware compression in the drive, compressing compressed file (or extremely small file, like couple of bytes) with gzip will produce larger file then original ;-) For example, try this: echo a a; ls -l a for a in 1 2 3 4 5; do gzip -v a; ls -l a.gz; mv a.gz a; done rm a Moral of the story, know your files before compressing them ;-) This message was sent using IMP, the Internet Messaging Program. --- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42 plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php ___ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
Re: [Bacula-users] Compression Exb-8900
Aleksandar Milivojevic wrote: Anyhow, if you have enough CPU power, I found that software compression (using gzip) does better job than hardware compression in the drive. Interesting -- this is the reverse of my experience. I've found hardware compression to give me comparable data compression and much faster actual throughput, with much lower host system CPU load. (And the host system is an AthlonXP 1700+, so it's no slouch.) -- Phil Stracchino [EMAIL PROTECTED] Renaissance Man, Unix generalist, Perl hacker Mobile: 603-216-7037 Landline: 603-886-3518 --- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42 plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php ___ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
Re: [Bacula-users] Compression Exb-8900
Quoting Phil Stracchino [EMAIL PROTECTED]: Aleksandar Milivojevic wrote: Anyhow, if you have enough CPU power, I found that software compression (using gzip) does better job than hardware compression in the drive. Interesting -- this is the reverse of my experience. I've found hardware compression to give me comparable data compression and much faster actual throughput, with much lower host system CPU load. (And the host system is an AthlonXP 1700+, so it's no slouch.) Well, it also depends on the actuall tape drive you have, and on the type of files being compressed. After all, there's theoreticall maximum the file can be compressed to, the closer you go to that theoreticall maximum, more CPU power you need (and it's growing exponentially, sometime a lot more CPU is needed to get only small decrease in compressed file's size). Compression algorithms in the drives are optimized to be primarly fast enough to compress at the speed data can be written to the tape, with actuall compression ratio being secondary objective. I probably needed to include usually and/or your experience may vary in my original text ;-) Gzip, on the other hand, is optimized to give high compression ratios at expense of the speed. You can tune it to some degree using -1 (fast, lower compression) to -9 (slow, higher compression) options, with default being -6 (slightly biased to better compression at expense of speed). The difference between -1 and -9 (in terms of speed) can be as big as two to three times (or negligable, depending on compressability and the size of actuall files being compressed). If you have very fast tape drives, and backing up single machine at a time, gzip might not be able to compress fast enough. On the other hand, if I'm not mistaken, software compression is done on the client side (in file daemon), so it is distributed. If you are doing several clients in parallel, you should be able to feed the drives with continous data stream. Plus, network bandwith consumed for your backup will be lower (for example, you are backing up machine on remote site over slow(er) link). So, both software and hardware compressions have their cons and pros, and there's really no definite answer which one is better. This message was sent using IMP, the Internet Messaging Program. --- This SF.Net email is sponsored by: Power Architecture Resource Center: Free content, downloads, discussions, and more. http://solutions.newsforge.com/ibmarch.tmpl ___ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
[Bacula-users] Compression Exb-8900
Hi, I have an Exabyte-8900 20/40 GB drive and it does a great job backing up my boxes. My question is: After about 25 GB, Bacula says the tape is full and wants another tape. According to the LCD display on the drive itself, compression is turned on. So, how can I tell Bacula to write up to 40 GB worth of data to the tape before changing? TIA, -- Trevor --- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42 plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php ___ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
Re: [Bacula-users] Compression Exb-8900
My experience with compression is that it doesn't work. I seldom get more than 5GB over the rated uncompressed capacity. _ _ _ _ ___ _ _ _ |Y#| | | |\/| | \ |\ | | | Ryan Novosielski - User Support Spec. III |$| |__| | | |__/ | \| _| | [EMAIL PROTECTED] - 973/972.0922 (2-0922) \__/ Univ. of Med. and Dent.| IST/AST - NJMS Medical Science Bldg - C630 Trevor Morrison wrote: Hi, I have an Exabyte-8900 20/40 GB drive and it does a great job backing up my boxes. My question is: After about 25 GB, Bacula says the tape is full and wants another tape. According to the LCD display on the drive itself, compression is turned on. So, how can I tell Bacula to write up to 40 GB worth of data to the tape before changing? TIA, --- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42 plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php ___ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
