On Sun, 24 May 2009 19:00:45 +0200 Thomas Glanzmann <thomas@xxxxxxxxxxxx> wrote: > Hello Ted, > I would like to know if there is already a mount option or feature in > ext3/ext4 that automatically overwrites freed blocks with zeros? If > this is not the case I would like to know if you would consider a > patch for upstream? I'm asking this because I currently do some > research work on data deduplication in virtual machine environments > and corresponding backups. It would be a huge space saver if there is > such a feature because todays and tomorrows backup tools for virtual > machine environments work on the block layer (VMware Consolidated > Backup, VMware Data Recovery, and NetApp Snapshots). This is not only > true for backup tools but also for running Virtual machines. The case > that this future addresses is the following: A huge file is > downloaded and later delted. The backup and datadeduplication that is > operating on the block level can't identify the block as unused. This > results in backing up the amount of the data that was previously > allocated by the file and as such introduces an performance overhead. > If you're interested in real live data, I'm able to provide them. > > If you don't intend to have such an optional feature in ext3/ext4 I > would like to know if you know a tool that makes it possible to zero > out unused blocks? > wouldn't it be better if the VM's would just support the TRIM command? -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
