[Techtalk] RAID data recovery w/ hardware controller

[Gina Feichtinger]

On 13.02.2008 19:19 Uhr, Rudy Zijlstra wrote:
> On Wed, 13 Feb 2008, Gina Feichtinger wrote:
[...]
>> May I ask what you mean with "partitioned raid driver"? I've had a
>> x-Series machine barf on me after install (a x3650 with RHEL AS to be
>> precise) only because in that case grub wasn't properly written to the
>> MBR...
> 
> Linux has two SW raid drivers. One which you cannot partition the array, 
> and one where you can parition the raid array like any other disk. The 
> latter is the most usefull IMHO, and not supported by either grub or 
> lilo....
> At least not half a year back when i last tried.

Hm, this sounds interesting, I should read up on it! What I forgot to
mention is I normally use LVM on top of the (mostly software) RAID
devices which gives me the flexibility I need :-)

>> A thing I found useful about SW RAID - switching to bigger disks in a
>> RAID-1 setup is pretty easy. Split the mirror, switch second disk,
>> rebuild RAID, switch first disk, rebuild RAID, done (OKOK, more or
>> less). I've had to do that a few times already when the internal 36GB
>> disks were getting too small.
> 
> No experience on this... And it needs more work anyway, and is also 
> depending on using a filesystem you can grow.

*nods* I've come to like ext2online for this. Minimum downtime and no
mandatory fsck before that as far as I have experienced so far.
<tangent>
Now if it only was possible to add new storage devices/disks on the fly
(e.g. in a SAN environment) I'd -truly- be happy with my servers in our
production environment!
</tangent>

[...]
>>> On SW raid, identifying which HDD has failed can be an issue. I've once
>>> lost a 1.5T array because we mis-identified which HDD had failed.... All
>>> data on the array was lost.
>>
>> May I ask how this happened? Ususally "cat /proc/mdstat" gives you a
>> good overview about the state of the array.
> 
> True, very true... But then, which cable represents which SATA port? 
> sometimes the port numbering on the SATA PCI cards is not exactly 
> logical... which caused the above mentioned mistake.
> 
> This card turned out to have the following numbering scheme: 1 3 4 2 (or 
> something simmilar). A later version from the same manufacturer has a 
> different scheme.

Ugh! I see how this can keep nasty surprises!

Cheers,

Gina
-- 
Gina Feichtinger                :: LinuxChix member
System-/SAN-Administrator & DBA :: http://www.linuxchix.org/
http://www.geekgrrl.priv.at/    :: LUGA member
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