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[dm-devel] Re: [PATCH] Add metadata writing and hot spare processing to hostraid driver in dmraid



On Fri, Mar 03, 2006 at 04:57:20PM -0800, Darrick J. Wong wrote:
> Hi all,

Hi Darrick.

> 
> Now that dmraid supports Adaptec HostRAID, I've turned my attention to 
> enabling support for writing metadata back to the disks, and 
> implementing rudimentary spare handling in RAID1 configurations.
> 
> The attached patch (which is admittedly very rough) does two key things. 

Will look into it on Mon.

>  First, it implements asr_write in a more meaningful manner than what's 
> in rc10 right now; with that part of the patch, dmraid gains the ability 
> to reconfigure an array while the system is running and save the changes 
> out to disk.  To do this, I had to change a struct to a pointer to a 
> struct in asr_reservedblock to to get write_metadata to work properly. 
> Also, it turns out that a few more things in asr_write had to happen 
> (and in the correct order) for writes to succeed.  If we fail to write 
> the metadata correctly, the HostRAID BIOS wipes the entire sector during 
> the next reboot.
> 
> The second part of the patch stores spare devices in a dummy .asr_spares 
> array.  When an I/O error is noticed (via event_io), a suitable spare 
> drive is pulled from the spare pool and inserted into the failing array.
> I haven't had a chance to test this code rigorously yet, because the 
> dmeventd portions of dmraid aren't implemented yet.
> 
> So, there are two things that I'd like to see added: online 
> reconfiguration support in dmraid (which I can now test via asr_write) 
> and online spare handling.  Heinz, are you working on either of these 
> features, or should I start writing them?

I am into device-mapper core work right now so please, go ahead :)

Heinz

> 
> --D


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Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Cluster and Storage Development                   56242 Marienrachdorf
                                                  Germany
Mauelshagen RedHat com                            +49 2626 141200
                                                       FAX 924446
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