On Thu, 26 Dec 2013 03:24:00 -0600 Stan Hoeppner [off-list ref]
wrote:

On 12/26/2013 2:55 AM, Christoph Hellwig wrote:

quoted

On Sat, Dec 21, 2013 at 05:18:42AM -0600, Stan Hoeppner wrote:

quoted

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.

IIRC you Dave C. and myself all voiced criticism after the default chunk
size was changed from 64KB to 512KB.  I guess we didn't make a strong
enough case to have it reduced, or maybe didn't use the right approach.

Maybe Neil is waiting for patches to be submitted for changing these
defaults, and to argue the merits in that context instead of pure
discussion?  Dunno.  Just guessing.  Maybe he'll read this and jump in.

Good guess.

NeilBrown