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 Fri, Aug 19, 2016 at 5:27 PM, Thor Lancelot Simon <tls%panix.com@localhost> wrote:
> On Thu, Aug 18, 2016 at 06:23:32PM +0000, Eduardo Horvath wrote:
> chunks.  Or to add support for that to RAIDframe.
...............
> That would help LFS and much more.  And you can do it without having
> to touch the LFS code.
>
I have been thinking about this, and I think that this is the best
option, although I like more integrate it with LFS as I said in my
previous mail, adding to RAIDframe it can be used/tested by more
people and it is possible that more developers/testers are involved.
Integrating it inside of LFS surely will be a one man project, that it
is very possible that it isn't finished.
Other bonus of integrating it with RAIDframe, it is can resolve the
problems of write hole of raid:
http://www.raid-recovery-guide.com/raid5-write-hole.aspx
I don't know if NetBSD resolves the problem of write hole (it has
penalty in performance to resolve it).
> However, there's stll the issue that this could effectively reorder
> reads around synchronous writes if you are not careful, particularly
> with the boot-time replay.  Ensuring that is right is probably the
> trickiest part by far.

If you can elaborate/explain this, it will be great. If
raidframe+nvram provides a coherent RAID with the commited writes, I
don't see possible problems with the LFS boot-time replay.