Re: Nvidia Raid5 Failure

[peter davidson <merrymeetpete@hotmail.com>]

Hi David,

For some reason this never made it through to my email inbox - I hop I haven't messed up the format as I have pulled the text in from a browser. Thanks (belatedly) for your response. I put some comments below.
 
>> Hi Folks,
>>
>> My computer suddenly shut down due to a failed memory module -
>> damaging the 1.8TB RAID5 array of three disks.
>>
>> The computer was able to boot with a degraded array (Windows 7 OS was
>> on the array) but I was unable to get the array to rebuild using the
>> Nvidia toolset - either at BIOS level or in Windows 7. Now the
>> computer will not boot from the array.
>>
>> I had something very similar to this happen a few weeks ago when the
>> mother board failed - I was able to limp things along to get a backup
>> of all important data.
>>
>> I am interested to know if LINUX will be able to recover the array
>> for me this time. Having got part way through this process before on
>> the previous failure (which led me to this forum), I am keen to
>> follow this through as an exercise knowing I have a backup of the
>> really important stuff.
>>
>> I intend to build LINUX onto a new disk and work through this in the
>> coming days - what would be my best choice of distro for this
>> exercise? I am hoping to find something that has all the relevant
>> tools and is relatively simple to get up and running with a friendly
>> GUI to help me navigate round.
>>
>> I used to work on various databases running on UNIX servers so I hope
>> I can still can find my way round a terminal window.
>>
>> Thanks in advance for any support anyone can offer me!
>>
>> Regards,
>>

>As a general point, don't do /anything/ to write to the disks or attempt
>to recover or rebuild them until you have copied off /all/ important
>data to safe backups.  If you have booted Windows from the array, then
>step one is to shut it down and do not even consider booting it until
>backups are all in place and double-checked.

On this note I was able to get the all useful data out to a couple of old disks. I have decided to hold off trying to reconstruct the array now until I get a second copy of the useful stuff on a new disk that I have ordered. Once everything is back together this new disk will be for my backup images to land on - strangely this whole thing started on the weekend I decided to get a proper backup of my data - what a coincidence! 

>
>You want to use a live CD for recovery here - it will let you play
>around with the disks without risking causing more damage.  My usual
>choice of Linux live CD for recovery purposes is System Rescue CD - I
>can't tell you if it is the best choice here, and I haven't needed to
>recover raid arrays using it.  But I find it very useful for testing and
>configuration, and have used it to recover data or fix up broken Windows
>systems.

I tried the Fedora live CD at first - this has dsadm but there was something missing (dm-raid45 module) that meant I could not use the command with my particular flavour of NVIDIA fake raid, the CD also didn't have mdraid. I then went on to download the Ubuntu live disk which had a crack at starting the array but didn't manage it - I really didn't like that it tried to load up the array without my being able to do anything about it - it also marked the array degraded and finally failed on a second start up that caused a kernel panic. I thought the idea of a Live CD was that it should be passive in terms of fiddling round with your existing disks and data at start up.

In my original question I was searching for a suitable LINUX install or live CD that would have everything on it I might need to get to work on the array. I went with the XUbuntu full installation on a seperate disk. It also didn't have mdadm but the OS was polite enough to tell me the exact command to issue to get it installed. This route therefore depends on an internet connection which proved tricky as the wireless adapter does not seam usable in any 64 bit OS. I got there in the end - good old fashioned network cables are very reliable!

>
>Another option you should consider is a Windows live CD.  You can't
>legally download and burn one, AFAIK, but there are plenty available if
>you are happy to look about.  There are also several Windows live CD
>generators that will make a bootable Windows CD from another windows
>machine, and can include utility programs.  They are particularly
>popular for malware recovery, but I expect you can put your Nvidia raid
>software on them.

None of the windows OSs can do anything to put the array together without the Nvidia support packages. Unfortunately now the Nvidia software won't rebuild the degraded array. The Nvidia tools provide no feedback on what is going on - you either succeed or fail in what you are trying to do - no tweaking allowed. So thats why LINUX looks a good option for this exercise.

>As for how well you can access the data and/or recover and/or rebuild
>your array from Linux, it all depends on the support for your Nvidia
>raid.  Someone here might have experience and can give you information,
>but your best starting point would be Nvidia's website.

Nvidia document their Windows GUI tools and give a few words on their BIOS utility - neither of these tools are able to put things straight from where things lie at the moment.

> There are Linux
>drivers and utilities for most proper hardware raid systems, but if this
>is a Nvidia-specific fake raid, it might not be supported.  Fake raid is
>not very popular in the Linux world - it combines the disadvantages of
>software raid with the disadvantages of hardware raid, and the benefits
>of neither.  It's only real advantage is if you want to use Windows with
>raid and don't want to pay for proper hardware raid.  Intel's "matrix"
>is far and away the most popular fake raid, and has good support in
>Linux, but I cannot say about Nvidia's raid.

I have read elsewhere that mdadm>=3 will cope with NVRAID - the fact that the Ubuntu Live CD had a good go at starting the array with madadm makes me think it is worth pursuing LINUX.

>
>
>If you want to set up a new system with Linux raid, then you will be
>able to get pointers and help in this list - but it's not really
>suitable for "how to get started with Linux" information.

I saw the further mails with Scot on this - I thought it would be on topic to ask for a Linux distro that would have everything I needed in place to get working with the array - as you can see from above I have been fumbling round with a few versions of LINUX and am dismayed at the sheer number available. Apologies if I led the forum away from its intended purpose.

> And if you
>want to mix Windows and Linux on the same system, be aware that Windows
>can't work with Linux software raid, and can't understand Linux
>filesystems (at least, not easily).  It is often much easier to keep
>them on separate machines and sharing files over the network.
>Alternatively, consider using VirtualBox to let you run one system as a
>virtual machine inside the other.

I like the idea of a NAS (or even an old machine on the network) running LINUX with the RAID on it. I have seen enough of nvraid fake raiding to say I want to get off there asap - or at the very least have a full backup and recovery procedure with redundancy in place to continue with it any further. 

>
>mvh.,
>
>David
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