On 3/4/13 5:20 PM, Mark Campbell wrote: > Oh, and while I'm thinking of it, what are your thoughts on using ZFS' dedup > feature on a BackupPC pool? I'm aware that a goodly amount of RAM would be > required for that feature. But since BackupPC's dedup feature is file-based, > and ZFS' dedup feature is block-based, even more space could be saved; > particularly when you're backing up things like .pst files, where a large > majority of the file is the same, save a few bytes/KB/MB. Such files are > flagged by BackupPC as different.
As long as you can keep the DDT in RAM, it would not slow down too much. You should test that, though. For about 1 TB of used disk space, I believe you would need something like 3 GB of RAM, depending on your filesystem's average block size. You can calculate the required RAM amount with "zdb -S trunk" which will simulate dedup on your disk, and then you can multiply the total blocks number by 320 to get the required RAM. If the dedup tables (DDTs) spill over your amount of available RAM, it will use the L2ARC if you have one or the disk if you don't have L2ARC cache. Harddisk access for the DDTs would slow you down significantly. If you can keep a pretty decent sized L2ARC on a very fast SSD it would be less slow if your RAM is too small. Also, like Tyler said, you should disable BackupPC's pooling to increase your performance. -- Best regards, Lars Tobias ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
