On Tuesday 2012-09-11 01:09, Martin Steigerwald wrote: >> > What about: >> > >> > - copy first backup version >> > - btrfs subvol create first next >> > - copy next backup version >> > - btrfs subvol create previous next >> >> Wouldn't "btrfs subvolume snapshot", plus "rsync --inplace" more >> useful here? That is. if the original hardlink is caused by multiple >> versions of backup of the same file. > >Sure, I meant subvol snapshot in above example. Thanks for noticing. > >But I do not use --inplace as it conflicts with some other rsync options I >like to use:
It is a tradeoff. rsync "--inplace" leads to fragmentation which is detrimental for the speed of reads (and read-write-cycles as used by rsync) of big files (multi-GB) that are regularly updated, but it is probably even worse for smaller-than-GB files because percent-wise, they are even more fragmented. $ filefrag */vm/intranet.dsk snap-2012-08-15/vm/intranet.dsk: 23 extents found snap-2012-08-16/vm/intranet.dsk: 23 extents found snap-2012-08-17/vm/intranet.dsk: 4602 extents found snap-2012-08-18/vm/intranet.dsk: 6221 extents found snap-2012-08-19/vm/intranet.dsk: 6604 extents found snap-2012-08-20/vm/intranet.dsk: 6694 extents found snap-2012-08-21/vm/intranet.dsk: 6650 extents found snap-2012-08-22/vm/intranet.dsk: 6760 extents found snap-2012-08-23/vm/intranet.dsk: 7226 extents found snap-2012-08-24/vm/intranet.dsk: 7159 extents found snap-2012-08-25/vm/intranet.dsk: 7464 extents found snap-2012-08-26/vm/intranet.dsk: 7746 extents found snap-2012-08-27/vm/intranet.dsk: 8017 extents found snap-2012-08-28/vm/intranet.dsk: 8145 extents found snap-2012-08-29/vm/intranet.dsk: 8393 extents found snap-2012-08-30/vm/intranet.dsk: 8474 extents found snap-2012-08-31/vm/intranet.dsk: 9150 extents found snap-2012-09-01/vm/intranet.dsk: 8900 extents found snap-2012-09-02/vm/intranet.dsk: 9218 extents found snap-2012-09-03/vm/intranet.dsk: 9575 extents found snap-2012-09-04/vm/intranet.dsk: 9760 extents found snap-2012-09-05/vm/intranet.dsk: 9839 extents found snap-2012-09-06/vm/intranet.dsk: 9907 extents found snap-2012-09-07/vm/intranet.dsk: 10006 extents found snap-2012-09-08/vm/intranet.dsk: 10248 extents found snap-2012-09-09/vm/intranet.dsk: 10488 extents found Without --inplace (prerequisite to use -S) however, it will recreate a file if it has been touched. While this easily avoids fragmentation (since it won't share any data blocks with the old one), it can take up more space with the big files. >-ax --acls --xattrs --sparse --hard-links --del --delete-excluded -- I knew short options would be helpful here: -axAXSH (why don't they just become the standard... they are in like almost every other rsync invocation I ever had) > -S, --sparse > Try to handle sparse files efficiently so they take up > less space on the destination. Conflicts with --inplace > because it’s not possible to overwrite data in a sparse > fashion. Oh and if anybody from the rsync camp reads it: with hole-punching now supported in Linux, there is no reason not to support "-S" with "--inplace", I think. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
