write-intent bitmaps

[Neil Brown]

On Sunday January 27, russell at coker.com.au wrote:
> http://lists.debian.org/debian-devel/2008/01/msg00921.html
> 
> Are they regarded as a stable feature?  If so I'd like to see distributions 
> supporting them by default.  I've started a discussion in Debian on this 
> topic, see the above URL for details.

Yes, it is regarded as stable.

However it can be expected to reduce write throughput.  A reduction of
several percent would not be surprising, and depending in workload it
could probably be much higher.

It is quite easy to add or remove a bitmap on an active array, so
making it a default would probably be fine providing it was easy for
an admin to find out about it and remove the bitmap is they wanted the
extra performance.

NeilBrown