Re: Tarsnap download speed

[Colin Percival <cperciva@tarsnap.com>]

Hi Daniel & list,

On 09/07/13 14:27, Daniel Parks wrote:
> I needed to access a backup last night and found that Tarsnap was downloading just under 1 megabit/second (measured with iftop filtered by the tarsnap port). Are these typical speeds?

Tarsnap extract performance is suboptimal due to the current design limiting
it to downloading one block at once -- that's ~ 64 kB per network round trip.
Usually this works out to a bit more than you're seeing though -- are you in
a distant corner of the world (from the perspective of the eastern USA)?

I'm working on rewriting code to remove this limitation; in the mean time, the
workaround is to run multiple extracts in parallel, since they will each get
the same one block per RTT performance.  Obviously you don't want to have
multiple tarsnap processes extracting the same data though -- but if your data
is organized so that you can have one process extract one directory and another
extract a different directory then it could speed things up significantly.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid