Re: time impact of the delta signature
andycapo--- via Dar-support <[email protected]>
| Newsgroups | gmane.comp.sysutils.backup.dar.support |
|---|---|
| Message-ID | <[email protected]> |
Hello Denis, > Il 22 febbraio 2019 alle 21.55 Denis Corbin <[email protected]> ha scritto: [...] > > Anyway, interim release 2.6.3.RC1 is available with a new option to > set the block size to use to build the signature. GIT is also up to > date on branch_2.6.x (both github and sourceforge) > > ftp://ftp.dm3c.org/dar.linux.free.fr/Interim_releases/ > > The default behavior is unchanged (2048 block size). if you want to > change this default, in place of --delta sig use --delta sig:<blocksize> > in your case "--delta sig:4M" > Thank you, for my usage on virtual machines images backup it is just perfect. By the way, also I do upload dar backups on the cloud, but as I showed with the tests, with the default signature block size, the dar signature time is longer than the cloud upload time for files larger than 5 GB. I'm using a librsync version 1.0 (default package as found in opensuse 15.0), maybe latest versions are more efficient. Will try build 2.0.2. [...] > > At a moment I intended to reserve low values like 2 and 3 as square > root and cube root of the filesystem but as file size are stored as > infinint (libdar internal type) I would have to implement those > mathematical function for this class... and on the other hand > computing these mathematical function for each file would cost CPU > more than necessary. > > Any idea is welcome, though :) > An efficient implementation of the approximated square root (rs_long_sqrt), here: https://bit.ly/2GXqpeV You may be interested in taking a look to this patch to librsync: https://bit.ly/2GLlsXB in particular commit https://bit.ly/2GGjXcS > > Regards, > Denis Best regards and thank you again! Andy