[CentOS] Some 3Ware questions

[Chris Mauritz]

Remco Barendse wrote:

> On Fri, 9 Sep 2005, Bryan J. Smith wrote:
>
>> Peter Arremann <loony at loonybin.org> wrote:
>>
>>> When initializing a raid 1, the controller wipes out all
>>> data according to the manuals. Every now and then you hear
>>> from people that say that the controller copies everything
>>> from disk1 to disk2 and if your IDE controller sector
>>> mapping matches what the 3ware controller does, you can
>>> keep your data in tact.
>>
>>
>> Actually, for RAID-1, 3Ware does _not_ using additional
>> blocking/organization, and does a direct mirror.  I.e., the
>> disks _can_ be used "normally."
>>
>> For RAID-0, 10 and 5, 3Ware uses 32KiB blocking and the
>> volumes are completely _unusable_ by anything else AFAIK
>> (maybe LVM2-MD?).
>
>
> That's not entirely correct. The 3Ware disks almost use standard raid 
> format, it's just the raid block on each disk that is written at the 
> end of the disk I believe instead of at the beginning. About a year a 
> go we rescued all data from a series of PATA disks from a friend of 
> mine when his 3Ware went bust. We were able to start the array in 
> software raid with the right parameters. Google was my friend then



I've also successfully rescued arrays when the 3ware card died by simply 
replacing the card and reboot.  The new card gloms the magic bits from 
the old array and just works.  Of course, this assumes that the 3ware 
card fails in a manner that doesn't involve scribbling random bits onto 
the array in its dying breaths....

Cheers,