Getting started the hard way with RAID

[Kevin O'Gorman]

On Sat, Dec 3, 2011 at 9:46 AM, Kevin O'Gorman <kogorman at gmail.com> wrote:
> On Sat, Dec 3, 2011 at 7:16 AM, Marius Gedminas <marius at pov.lt> wrote:
>> On Fri, Dec 02, 2011 at 09:44:28AM -0800, Kevin O'Gorman wrote:
>>> On Fri, Dec 2, 2011 at 1:30 AM, Marius Gedminas <marius at pov.lt> wrote:
>>> > On Thu, Dec 01, 2011 at 06:56:30PM -0800, Kevin O'Gorman wrote:
>>> >> I'm in the late stages of recovering a broken system.  The original
>>> >> had a hardware raid controller managing a mirror set that contained
>>> >> some stuff that was not backed up. Fortunately, one reason it wasn't
>>> >> backed up is that it wasn't really vital.  Nevertheless, I'd like to
>>> >> get at that stuff.
>>> >>
>>> >> The hard part is that I no longer have that RAID controller, just the
>>> >> two drives.  The controller was a 64-bit PCI card, and the new mobo
>>> >> cannot handle it.
>>> >
>>> > Have you googled for the model and manufacturer of that RAID controller?
>>>
>>> Not yet, but I will.  It was a 3ware 9550SX controller.
>>
>> $ dmraid -l
>> asr     : Adaptec HostRAID ASR (0,1,10)
>> ddf1    : SNIA DDF1 (0,1,4,5,linear)
>> hpt37x  : Highpoint HPT37X (S,0,1,10,01)
>> hpt45x  : Highpoint HPT45X (S,0,1,10)
>> isw     : Intel Software RAID (0,1,5,01)
>> jmicron : JMicron ATARAID (S,0,1)
>> lsi     : LSI Logic MegaRAID (0,1,10)
>> nvidia  : NVidia RAID (S,0,1,10,5)
>> pdc     : Promise FastTrack (S,0,1,10)
>> sil     : Silicon Image(tm) Medley(tm) (0,1,10)
>> via     : VIA Software RAID (S,0,1,10)
>> dos     : DOS partitions on SW RAIDs
>>
>> No 3ware here.  A quick Google seems to confirm that dmraid is mostly
>> for fakeraid devices, while 3ware is a real hardware RAID controller.
>>
>> (I'm not sure what the difference is -- so the RAID logic runs on an
>> embedded CPU on the daughter card instead of your main CPU, which makes
>> performance better, but why would that have any impact on on-disk
>> metadata formats?)
>>
>> Looks like you may need to buy a 3ware RAID card if you want to recover
>> your data.
>
> Maybe not.  I just worked up the courage to try dmraid.  So far, I've
> only tried discovery, but it's promising:
> root at treat:~# dmraid -r
> /dev/sdd: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
> /dev/sdb: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
> root at treat:~#
>
> That's exactly the two disks that had the mirror halves, and the size
> is convincing.  I don't understand everything it's showing, and I
> haven't had the courage to actually turn it on yet....

With a little more courage, I tried and failed.

  root at treat:~/work# dmraid -r
  /dev/sdd: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
  /dev/sdb: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
  root at treat:~/work# dmraid -ay
  ERROR: ddf1: wrong # of devices in RAID set "ddf1_SimpleVol" [2/1] on /dev/sdd
  ERROR: ddf1: wrong # of devices in RAID set "ddf1_SimpleVol" [2/1] on /dev/sdb
  RAID set "ddf1_SimpleVol" was not activated
  root at treat:~/work#

In fact, I find the man page for dmraid very confusing and have been
unable to get any other commands to even try...

For instance, to display data "dmraid -r" works and so does "dmraid
-rc", but further embellishments fail.
-- root at treat:~/work# dmraid -r --display_columns=ser
*ERR*
*ERR*
root at treat:~/work# dmraid -r --display_columns=d
*ERR*
*ERR*
root at treat:~/work#

And so it goes.  I'll be looking for other documentation as soon as I
finish figuring out ufw enough so that I can have a firewall and a web
page at the same time.  It appears to me that the man pages for the
more advanced stuff were not meant for human consumption...

Kevin O'Gorman, PhD