Les Mikesell <firstname.lastname@example.org> wrote on 09/18/2012
> On Tue, Sep 18, 2012 at 1:14 PM, Timothy J Massey <email@example.com>
> > I have just performed some full backups on a host after disabling
> > compression. Results:
> > Not-first backup with compression: 139.9 minutes for 70000.6
> > First backup without compression: 76.7 minutes for 70181.5
> > Second backup without compression: 36.6 minutes for 70187.4
> > Wow: Four times the performance. Looks like compression
> > *significant* performance-eater.
> Can you repeat those the 3rd time with checksum-caching enabled so
> have a better idea of how much time that saves? (If you didn't
> it on already, you'd need to repeat again to store them first)
The host I was playing with is a bad one for that:
it's a pretty visible host, and about 30% of the data changes constantly.
I've selected another host to experiment with. One issue is
that it's three times as large, so each full backup is slower. Good
news is that it's an unused server, so 99.99% of the data is static, and
no one cares if I hammer the server for no real reason! :)
I just ran a first backup of that host with compression
disabled, and it took the same amount of time as not-first fulls were taking
with compression. The backup server is busy right now and probably
for the next 2 or so hours. Once it's free, I will start a second
non-compression full and we'll see how it goes.
Right now, still no hash caching. Once I gather
the stats for non-compression only, I will add in hash caching and we'll
see from there.