create metadata from DMRAID

Fang, Ying ying.fang at
Fri Jun 29 00:23:10 UTC 2007

Thanks, Heinz. I'd like to estimate the work if I add the creation
function in DMRAID. Please help me figure out the changes.

Based on my understanding, a metadata handler is designed to provide
data or receive messages via "struct dmraid_format" and use dmraid
internal functions via format.c while Struct lib_context carries the
information center. Correct me if I'm wrong here.
1. Is a metadata handler designed to use .write operation to create or
delete a raid set? Can I add .create and .delete in "struct
2. A metadata handler needs build metadata based on several data such as
raid set name, raid level, size, etc. Can they be carried into as a
string argument or a field in "struct lib_context"? It's possible to
build disk sets, raid device sets, and raid set sets too.
3. Can I design my own option format to create metadata by DMRAID such
as:"dmraid -ms isw_xxxxxx_raidSet1" (d and D have been used.) to delete
a raid set and "dmraid -f isw -w "isw_xxxx_raidNewSet device-mapper
format" where device-mapper format is "0 1028160 striped 2 256 /dev/sdb
0 /dev/sdc 0". But I have trouble for nested raid setup and try to use
raid10 or raid51 to identify it. 

Anyway, are there any other requirements for DMRAID design? They would
be helpful to guide my design.

I appreciate your inputs.


-----Original Message-----
From: Heinz Mauelshagen [mailto:mauelshagen at] 
Sent: Thursday, June 28, 2007 2:11 AM
To: ATARAID (eg, Promise Fasttrak, Highpoint 370) related discussions
Cc: Fang, Ying
Subject: Re: create metadata from DMRAID

On Wed, Jun 27, 2007 at 03:38:32PM -0700, Fang, Ying wrote:
> Hi,
> I'm going to provide a function to create isw metadata and looking for
> better approach as I have two choices: add the function in dmraid or
> application running on top of dmraid. The pro of the former one is
> the function will be eventually included in dmraid and distributed by
> RedHat while a stand along utility may not be maintained well in the
> future. The con is the acceptance of my implementation as the current
> source code hasn't set up much ground work on this function yet. I'm
> concerned if I can fulfill the task in a month. I'm looking forward to
> your advice. 

Of course the earlier is the preferred choice, because it'll leverage
code to be suitable for other metadata format handlers as well.

I you've got such time constraint, you may be forced to go for an
interim stand alone tool and we'll migrate the code essentials into
dmraid later...


> Thanks,
> Ying 

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Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Storage Development                               56242 Marienrachdorf
Mauelshagen at                            PHONE +49  171 7803392
                                                  FAX   +49 2626 924446

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