md-RAID5/6 stripe_cache_size default value vs performance vs memory footprint

[Christoph Hellwig]

On Sat, Dec 21, 2013 at 05:18:42AM -0600, Stan Hoeppner wrote:
> The powers that be, Linus in particular, are not fond of default
> settings that create a lot of kernel memory structures.  The default
> md-RAID5/6 stripe_cache-size yields 1MB consumed per member device.

The default sizing is stupid as it basically makes RAID unusable out
of the box, I always have to fix that up, as well as a somewhat
reasonable chunk size for parity RAID to make it usable.  I'm also
pretty sure I complained about it at least once a while ago, but never
got a reply.