On Sun, Sep 29, 2013 at 10:27 AM, Colin Percival <cperc...@tarsnap.com> wrote: > On 09/29/13 06:26, Yonatan Broza wrote: >> I'm using tarsnap to backup around 22GB in 22K files. >> >> There's hardly any difference between backups (verified using diff) yet >> tarsnap >> reports 12MB of new data. >> >> Most timestamps are changed since most of the files are recreated before each >> backup. >> >> What's the reason for the large amount of new data? > > Tarsnap stores a 512-byte tar header for each file, and this header includes > the > file modification time. 22,000 files x 512 bytes/file = 11.2 MB, so this > looks > like the reason for the new data you're seeing. >
Aha! Is there an easy way to turn that off? I archive a fair amount of autogenerated data, and the timestamps are completely worthless as far as I'm concerned. --Andy > The good news is that tar headers tend to compress very well, so the data > you're > actually uploading -- the *compressed* new data -- is almost certainly much > less > than that. > > -- > Colin Percival > Security Officer Emeritus, FreeBSD | The power to serve > Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid -- Andy Lutomirski AMA Capital Management, LLC
