Re: Change Chunk Size on Array?

[SandeepKsinha <sandeepksinha@gmail.com>]

On Wed, May 13, 2009 at 10:15 AM, Neil Brown <neilb@suse.de> wrote:
> On Tuesday May 12, sandeepksinha@gmail.com wrote:
>>
>>
>>
>> crshman wrote:
>> >
>> > Hello All,
>> >
>> > I wanted to know if it were possible to change the chunk size on an array
>> > after it has been created. I have a software raid 5 comprised of 7 drives
>> > with a chunk size of 64k. I wanted to up that to 1024k, would this be
>> > possible without losing any data? This isn't mission critical so it is ok
>> > if i need to stop the array first, however I'd rather not lose any data.
>> >
>> It is possible to change the chunksize but for the same you would need to
>> offline your array.
>
> Is it?  How?
>

That was all that I could read from" RAID on Linux" by Derek Vadala, Page 118.

It mentions that this could be achieved by offlining the array and
using "raidreconf".
He also mention chances of data loss and also the caveats of "raidreconf".


> Online changing of chunk size for raid5 is very close to being
> implemented.
> All the kernel side support will be in 2.6.30.
> I just need to spend some time getting mdadm to make it work.
> Because data is being rearranged in-place, and because you don't want
> to lose everything if your systems crashes, mdadm will have to work in
> tandem with the kernel making a backup copy of a section of the array,
> allowing the kernel to reshape that section, and then moving on to the
> next section.  It will be slow, but it will be reliable.
>
> NeilBrown
>



-- 
Regards,
Sandeep.





 	
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