On 03/20/2014 04:35 PM, Bernd Schubert wrote:

quoted

Yes.  The article gives 16384 and 32768 as examples for
stripe_cache_size.  Such high values tend to reduce throughput instead
of increasing it.  Never use a value above 2048 with rust, and 1024 is
usually optimal for 7.2K drives.  Only go 4096 or higher with SSDs.  In
addition, high values eat huge amounts of memory.  The formula is:

Why should the stripe-cache size differ between SSDs and rotating disks?
Did you ever try to figure out yourself why it got slower with higher
values? I profiled that in the past and it was a CPU/memory limitation -
the md thread went to 100%, searching for stripe-heads.

Sorry, I forgot to write 'cpu usage', so it went to 100% cpu usage.

So I really wonder how you got the impression that the stripe cache size
should have different values for differnt kinds of drives.


Cheers,
Bernd