Re: What is the best layer/device for a write-back cache based in nvram?

[Jose Luis Rodriguez Garcia <joseyluis%gmail.com@localhost>]

>> 1- There is no need to use parity map for the RAID 1/10/5/6. Usually
>> the impact is small, but it can be noticeable in busy servers.
>I don't notice it.
When there is a crash, the time to rebuild the raid < 1min?

...
>rather large. A segment should match a slice (or a number of them)
>I would suppose LFS to perform great on a RAIDframe. Isn't Manuel Bouyer
>using this in production?
This is the idea, but when there is a fsync, it must be written to
disk. Therefore there are small segments inside of one "physical
segment"

Also LFS is still far from being stable.

>> 4- Faster synchronous writes.
>Y E S.
>This is the only point I fully aggree on. We've had severe problems with
>brain-dead software (Firefox, Dropbox) performing tons of synchronous 4K
>writes (on a bs=16K FFS) which nearly killed us until I wrote Dotcache
(>http://www.math.uni-bonn.de/people/ef/dotcache) and we set XDG_CACHE_HOME
>to point to local storage.

This one is the last point in my list, but this is the obvius
adventage of any write cache