Re: IIs factible to implement full writes of strips to raid using NVRAM memory in LFS?

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

On Thu, Aug 18, 2016 at 7:24 PM, Eduardo Horvath <eeh%netbsd.org@localhost> wrote:
>
> LFS writes the metadata at the same time, in the same place as the data.
> No synchronous writes necessary.

As I understand LFS needs to do synchronous writes when there is
metadata operations (directories)/fsync operations involved. Instead
of writting a full segment (1 MB per default), it writes a "small
segment". It kills performance in RAID 5/6, because the write isn't a
full stripe: you have to read all the disks, for calculate the new
parity 1 write on raid of x disks= x reads + 2 writes (data + parity).

The NVRAM memory solves this problem as buffer/ write cache.

>
> The problem is that LFS is less a product than a research project:
Yes I know this. But it seems that it was near stable in previous
versions: 1.6 and 4.0 of NetBSD. David Holland is slowly solving some
of these problems (most of a MP kernel). I also wan to to give my
small help.

>
> Anyway, hacking on LFS is lots of fun.  Enjoy!
This is true. I want to contribute to a great project as NetBSD.