RFC: GEOM MULTIPATH rewrite

[Stephane LAPIE]

Hello,

First of all, many thanks. I am going to test your patch on 9.0-RC1, and
try to backport it to 8.2 (which is the main version I am currently
using at work, in the environment where I have a critical need for FC
multipath redundancy...)

Again, thanks for your efforts. I hope to be giving feedback soon.

Cheers,

On 11/01/2011 05:10 AM, Alexander Motin wrote:
> Hi.
> 
> Attempt to fix some GEOM MULTIPATH issues made me almost rewrite it. So
> I would like to present my results and request for testing and feedback.
> 
> The main changes:
>  - Improved locking and destruction process to fix crashes in many cases.
>  - Improved "automatic" configuration method to make it safe by reading
> metadata back from all specified paths after writing to one.
>  - Added provider size check to reduce chance of conflict with other
> GEOM classes.
>  - Added "manual" configuration method without using on-disk metadata.
>  - Added "add" and "remove" commands to manage paths manually.
>  - Failed paths no longer dropped from GEOM, but only marked as FAIL and
> excluded from I/O operations.
>  - Automatically restore failed paths when all others paths are marked
> as failed, for example, because of device-caused (not transport) errors.
>  - Added "fail" and "restore" commands to manually control FAIL flag.
>  - GEOM is now destroyed on last provider disconnection. IMHO it is
> right to do if device was completely removed.
>  - Added optional Active/Active mode support. Unlike Active/Passive
> mode, load evenly distributed between all working paths. If supported by
> device, it allows to significantly improve performance, utilizing
> bandwidth of all paths. It is controlled by -A option during creation.
> Disabled by default now.
>  - Improved `status` and `list` commands output.
> 
> Latest patch can be found here:
> http://people.freebsd.org/~mav/gmultipath4.patch
> 
> Feedbacks are welcome!
> 
> Sponsored by: iXsystems, Inc.
> 

-- 
Stephane LAPIE, EPITA SRS, Promo 2005
"Even when they have digital readouts, I can't understand them."
--MegaTokyo

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