Re: Raid 5 Array

[Simon Mcnair <simonmcnair@gmail.com>]

One last thing.... I've never heard of anyone using a raid 05. Why
wouldn't you use a RAID50 ?  Please can you dish the dirt on what
benefit there is ? (I would have thought a raid50 would have been
better with no disadvantages ?). I thought that raid10 & 50 were the
main ones in use in 'the industry'.

Please forgive me if I'm showing my ignorance.

Simon
On 2 Apr 2011, at 21:09, Simon McNair <simonmcnair@gmail.com> wrote:

> cc'd the list back in as I'm not an md guru.
>
> I did a search for mdadm raid 50 and this looked the most appropriate.
>
> http://books.google.co.uk/books?id=DkonSDG8jUMC&pg=PT116&lpg=PT116&dq=mdadm+raid+50&source=bl&ots=Ekw6NCiXqR&sig=edBYg9Gtd5RXyuUU0PeSpHvS7pM&hl=en&ei=9YGXTYyeBcGFhQe90ojpCA&sa=X&oi=book_result&ct=result&resnum=5&ved=0CEIQ6AEwBA#v=onepage&q=mdadm%20raid%2050&f=false
>
> Simon
>
> On 02/04/2011 20:38, Marcus wrote:
>> Yes I used --zero-superblock this time. I think that was my problem
>> last time it kept detecting the drives at random and creating odd
>> arrays. This time I am not sure what my problem is. I got two drives
>> back up so I have my data back but I tried getting the two raid0
>> drives to become part of the raid5 twice so far and each time fdisk -l
>> shows the wrong sizes for the raids when they are combine the first
>> time it showed the small raid as 1TB which is the size of the big raid
>> the second time it showed the big raid as 750GB which is the size of
>> the small array. Some how the joining of the two raids is corrupting
>> the headers and reporting wrong information.
>>
>> Is there a proper procedure for creating a raid0 to put into a raid5?
>> last time I created my raid0 and added a partition to the raids and it
>> automatically dropped the partition and just showed md0 and md1 in the
>> array instead of md0p1 and md1p1 which was the partition i added to
>> the array. I have tried adding the partition into the array and I also
>> tried adding just array into the array. neither method seems to be
>> working this time.
>>
>> On Sat, Apr 2, 2011 at 12:01 PM, Simon McNair<simonmcnair@gmail.com>  wrote:
>>> Hi,
>>> I'm sure you've tried this, but do you use --zero-superblock before moving
>>> disks over ?
>>>
>>> Simon
>>>
>>> On 02/04/2011 19:51, Marcus wrote:
>>>> I have a raid array this is the second time an upgrade seems to have
>>>> corrupted the array.
>>>>
>>>> I get the following message from dmesg when trying to mount the array
>>>> [  372.822199] RAID5 conf printout:
>>>> [  372.822202]  --- rd:3 wd:3
>>>> [  372.822208]  disk 0, o:1, dev:md0
>>>> [  372.822212]  disk 1, o:1, dev:sdb1
>>>> [  372.822216]  disk 2, o:1, dev:sdc1
>>>> [  372.822305] md2: detected capacity change from 0 to 1000210300928
>>>> [  372.823206]  md2: p1
>>>> [  410.783871] EXT4-fs (md2): Couldn't mount because of unsupported
>>>> optional features (3d1fc20)
>>>> [  412.401534] EXT4-fs (md2): Couldn't mount because of unsupported
>>>> optional features (3d1fc20)
>>>>
>>>> I originally had a raid0 md0 with two 160GB drives, a raid0 md1 with
>>>> 250GB and md0, a raid 5 with a 1.0TB, 500GB, and md1
>>>>
>>>> I swapped out md1 with a new 1TB drive which worked. then i dropped
>>>> the 500GB and combined it with the 250GB drive to make a 750GB drive
>>>>
>>>> The error seems to come when you reintroduce drives that were
>>>> previously in a raid array into a new raid array. This is the second
>>>> time I have ended up with the same problem.
>>>>
>>>> Any suggestions on how to recover from this or is my only option to
>>>> reformat everything and start again?
>>>> --
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