On Thu, 22 May 2014 06:31:58 +0200 George Duffield <forumscollective@xxxxxxxxx> wrote: > I have a RAID5 array comprised of 4 x 3TB Seagate 7200 RPM SATAII > drives. The array was created on Ubuntu Server running on a HP > Microserver N54L using the following command: > > sudo mdadm --create --verbose /dev/md0 --raid-devices=4 --level=5 > /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 > > Formatted using: > mkfs.ext4 -b 4096 -E stride=128,stripe-width=384 /dev/md0 > > The array is mounted in /etc/fstab by reference to its UUID and is now > near full. > > A few days back I turned on the server to access some of the files > stored on it when I found the server was not present on the network. > Inspecting the actual server (connected kb & monitor) I noticed that > the machine had not progressed beyond the BIOS post screen – one of > the drives had become damaged (2nd drive in same slot in same > Microserver to be damaged the same way – drive spins up fine, machine > knows it's there, but can't communicat successfully with the drive). > In any event, suffice it to say the drive is history – it and the > Microserver will be RMAd when this is over. > > So, I'm now left with a degraded array comprising 3x3TB drives. I've > purchased a replacement drive (same make and model) in the interim > (and I've yet to boot this machine with the old drive removed or the > new one inserted i.e. from an OS standpoint Ubuntu/mdadm does not yet > know the array is degraded). > > As I've lost complete faith in the Microserver (and it may very well > damage the new drive during recovery of the array) I've also purchased > and assembled a 2nd machine with 6 on board SATA ports rather than > rely on another Microserver. My intention is to remove the drives > from the Microserver and install them in the new machine (which I'll > boot off the same USB flash drive I used to boot the Microserver from > [to further complicate things it seems my flash drive may also be > corrupted, so I may have to recover from a fresh Ubuntu install and > reassemble the array]). > > A few questions if I may: > - Is moving the array to another computer and recovering it on the new > computer running Ubuntu Server likely to present any particular > challenges? No. If you were trying to boot of the array that you moved it might be interesting. But as you aren't I cannot see any possible issue (assuming the hardware functions correctly). > > - Does the order/ sequence of connection of the drives to the > motherboard matter? No. > > Another way of asking the aforementioned question is whether mdadm > would care if one swapped drives in Microserver backplane/ PC SATA > ports such that the physical backplane slot/ SATA port that one/more > of the drives occupies differs from that it occupied when the array > was created? No. mdadm looks at the content of the devices, not their location. > > - How would I best approach rebuilding the array, my current thinking > is as follows: > = Identify with certainty which drive has failed - this will be done > by removing the OS flash drive from the Microserver and disconnecting > all drives from the backplane other than the one I believe is faulty > (first slot on backplane) and booting the machine. The failed drive > causes a POST failure and is thus easily identified. > = Remove all drives from the Microserver and install into new PC > referenced above, at the same time replacing the failed drive with the > replacement I purchased > = Powering new PC via UPS > = Booting the PC from the flash drive > = Allowing the degraded array to be assembled by mdadm when prompted at boot > = Adding the replacement drive to the array and allowing the array to > be re-synchronized > = If I'm not able to access the flash drive I will create a fresh > install of Ubuntu Server and attempt to recreate the array in the > fresh install. > > All thoughts/ comments/ guidance much appreciated. Sounds good. Though I would discourage the boot sequence from assembling the degraded array if possible. Just get the machine up with the drive untouched. Then use "mdadm -E" to look at each device and make sure they are what you think they are (e.g. consistent Event numbers etc). Then mdadm --assemble /dev/mdWHATEVER ..list-of-devices... Then make sure that looks good. Then mdadm /dev/mdWHATEVER --add new-device NeilBrown > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html
Attachment:
signature.asc
Description: PGP signature
