Re: New data reported too big

[Andy Lutomirski <luto@amacapital.net>]

On Sun, Sep 29, 2013 at 10:27 AM, Colin Percival <cperciva@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