Some filesystem performance numbers

[Slawa Olhovchenkov]

On Tue, Jan 13, 2015 at 05:30:54PM -0500, Garrett Wollman wrote:

> I recently bought a copy of the SPECsfs2014 benchmark, and I've been
> using it to test out our NFS server platform.  One scenario of
> interest to me is identifying where the limits are in terms of the
> local CAM/storage/filesystem implementation versus bottlenecks unique
> to the NFS server, and to that end I've been running the benchmark
> suite directly on the server's local disk.  (This is of course also
> the way you'd benchmark for shared-nothing container-based
> virtualization.)
> 
> I have found a few interesting results on my test platform:
> 
> 1) I can quantify the cost of using SHA256 vs. fletcher4 as the ZFS
> checksum algorithm.  On the VDA workload (essentially a simulated
> video streaming/recording application), my server can do about half as
> many "streams" with SHA256 as it can with fletcher4.

For VDA recordsize=1M (or more) can give performance impcat in case
saturated HDD by IOPS.

> 2) Both L2ARC and separate ZIL have small but measurable performance
> impacts.  I haven't examined the differences closely.

This is depend of fractions hot/warm/cold content.

> 3) LZ4 compression also makes a small performance impact, but as
> advertised, less than LZJB for mostly-incompressible data.
> 
> I hope to be able to present the actual benchmark results at some
> point, as well as some results for the other three workloads.
> 
> -GAWollman
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