[OpenIndiana-discuss] Useful tidbit for ZFS backup via ZFS Send

[Jim Klimov]

2012-09-29 21:42, Martin Bochnig wrote:
> thank you for sharing this!
> Very interesting. It shall help a lot.
> Especially on older multisocket systems like on Ultra 80, it will
> probably make a substantial difference.

I'm sure I posted an RFE about pigz and pbzip2 in illumos
bugtracker, but can't find it anymore - guess I was imagining
things or networking was lost at an unfortunate moment :\

Anyway, my wife's university thesis was about multithreading
on example of Niagara CPUs, and pigz/pbzip2 were among the
test subjects - showing a linear improvement in speed with
utilization of all cores, a "slower" linear upon utilization
of all threads ("strands") on a single core, and a multiplied
mix of the two if equal numbers of threads on all cores were
utilized. Overall, a 4-strand utilized core on UltraSPARC T1
provided about 2.4x the performance of a single-strand core,
which is a nice boost for essentially inexistant and "free"
transistor count (what, some registers to remember state?)

Given that single-core performance of T1 and T2 sucked, such
ways of parallelization of singular tasks were a very good
way to even ourperform some few-core Xeons and Opterons of
that time, in terms of wallclock time needed to complete a
task such as compression of a large archive. In regular
backups, this is not such an infrequent task to be dismissed.

Also, IIRC, 64-bit variants did perform slower and had no
benefits since you can always redirect IO through pipes.

HTH,
//Jim