[arch-general] Software RAID w/ 4 Drives Fails
I am successfully able to install Arch Linux with 3 drives in a RAID5 array on Arch Linux using: mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sda2 /dev/sdb2 /dev/sdc2 Now when I attempt the install with 4 physical disks and add the same command above with just attaching /dev/sdd2 and changing the # of devices from 3 to 4, I get a failure. When I reboot the system I lose keyboard and it asks me to enter a run level. Obviously I can't troubleshoot more because I have no keyboard. What command should I use to create a RAID5 with more disk space (no hot spare) using 4 drives? My commands and install method work perfect with 3 drives but 4 and the system crashes upon reboot. Any tips?
I'm not sure why it is failing to boot for you with 4 drives but you may want to try completing the install with 3 drives and then add the fourth drive to your array after a successful reboot. J On 01/22/2010 11:13 AM, Carlos Williams wrote:
I am successfully able to install Arch Linux with 3 drives in a RAID5 array on Arch Linux using:
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sda2 /dev/sdb2 /dev/sdc2
Now when I attempt the install with 4 physical disks and add the same command above with just attaching /dev/sdd2 and changing the # of devices from 3 to 4, I get a failure. When I reboot the system I lose keyboard and it asks me to enter a run level. Obviously I can't troubleshoot more because I have no keyboard.
What command should I use to create a RAID5 with more disk space (no hot spare) using 4 drives? My commands and install method work perfect with 3 drives but 4 and the system crashes upon reboot.
Any tips?
On Fri, Jan 22, 2010 at 11:13 AM, Carlos Williams <carloswill@gmail.com> wrote: snip
When I reboot the system I lose keyboard and it asks me to enter a run level. Obviously I can't troubleshoot more because I have no keyboard.
snip
Any tips?
Sorry I can't help you with your RAID. I have a RAID 5 with 3 drives and like you said, that works. About loosing your keyboard. Do you have a USB keyboard ? If so, do you have "usbinput" in your /etc/mkinitcpio.conf ? -- Louis Brazeau Informaticien
Can you add a drive to an array after it has been built? I know you can add a hot spare, or remove a drive and add another, but I did not think you could increase N, where the size of the array is N-1 * size of each drive. How is the raid going to know which is data and which is parity? Of course I could be wrong. On Fri, Jan 22, 2010 at 12:03 PM, Louis Brazeau <lbrazeau@gmail.com> wrote:
On Fri, Jan 22, 2010 at 11:13 AM, Carlos Williams <carloswill@gmail.com> wrote:
snip
When I reboot the system I lose keyboard and it asks me to enter a run level. Obviously I can't troubleshoot more because I have no keyboard.
snip
Any tips?
Sorry I can't help you with your RAID. I have a RAID 5 with 3 drives and like you said, that works.
About loosing your keyboard. Do you have a USB keyboard ? If so, do you have "usbinput" in your /etc/mkinitcpio.conf ?
-- Louis Brazeau Informaticien
RAID5 is one of the levels that can be added to after creation. I think you should boot from the install CD and read the mdadm man page. It contains all the information you need to do what you want. That said, when you try to build the 4-drive array, do you get any errors reported? You may need to set the partition type to Linux MD RAID for the new drive if you intend to use the mdadm hook to assemble the array. On Jan 22, 2010 1:15 PM, "Dwight Schauer" <dschauer@gmail.com> wrote: Can you add a drive to an array after it has been built? I know you can add a hot spare, or remove a drive and add another, but I did not think you could increase N, where the size of the array is N-1 * size of each drive. How is the raid going to know which is data and which is parity? Of course I could be wrong. On Fri, Jan 22, 2010 at 12:03 PM, Louis Brazeau <lbrazeau@gmail.com> wrote:
On Fri, Jan 22, 2010...
On Fri, Jan 22, 2010 at 2:34 PM, Robert Howard <rjh0507@ecu.edu> wrote:
RAID5 is one of the levels that can be added to after creation. I think you should boot from the install CD and read the mdadm man page. It contains all the information you need to do what you want. That said, when you try to build the 4-drive array, do you get any errors reported? You may need to set the partition type to Linux MD RAID for the new drive if you intend to use the mdadm hook to assemble the array.
On Jan 22, 2010 1:15 PM, "Dwight Schauer" <dschauer@gmail.com> wrote:
Can you add a drive to an array after it has been built?
I know you can add a hot spare, or remove a drive and add another, but I did not think you could increase N, where the size of the array is N-1 * size of each drive. How is the raid going to know which is data and which is parity?
Of course I could be wrong.
I don't doubt that I could build a working Arch system with 3 physical drives and then use 'mdadm' to add the 4th drive as a spare or as additional disk space for the RAID5 array. I should be able to add a 4th disk to RAID5 w/o having any 'hot spares, correct? I just feel that I should be able to do this from a fresh install. I assumed I was missing a syntax in the command. I partition all 4 disks identical. All disks have a equal amount of partition space assigned to RAID (type = fd) and then I use mdadm to build the array so I can't see why it does not work. Yes I do have a USB keyboard but if I don't need to add the usb modules for RAID5 with 3 disks, why would I need to add it for RAID5 with 4 disks. It makes no sense to me...
Yes, you should be able to do it either way. I have built 6+ drive arrays from clean install before without any problem. IIRC, the command should just be mdadm /dev/md0 -level=5 -raid-devices=4 /dev/sd[a-d]1 You can also add a switch to force all drives active but you must also add -ff to the command line. On Jan 22, 2010 3:56 PM, "Carlos Williams" <carloswill@gmail.com> wrote: On Fri, Jan 22, 2010 at 2:34 PM, Robert Howard <rjh0507@ecu.edu> wrote: > RAID5 is one of the levels... I don't doubt that I could build a working Arch system with 3 physical drives and then use 'mdadm' to add the 4th drive as a spare or as additional disk space for the RAID5 array. I should be able to add a 4th disk to RAID5 w/o having any 'hot spares, correct? I just feel that I should be able to do this from a fresh install. I assumed I was missing a syntax in the command. I partition all 4 disks identical. All disks have a equal amount of partition space assigned to RAID (type = fd) and then I use mdadm to build the array so I can't see why it does not work. Yes I do have a USB keyboard but if I don't need to add the usb modules for RAID5 with 3 disks, why would I need to add it for RAID5 with 4 disks. It makes no sense to me...
On Wed, Jan 27, 2010 at 8:12 AM, Robert Howard <rjh0507@ecu.edu> wrote:
Yes, you should be able to do it either way. I have built 6+ drive arrays from clean install before without any problem.
IIRC, the command should just be mdadm /dev/md0 -level=5 -raid-devices=4 /dev/sd[a-d]1
You can also add a switch to force all drives active but you must also add -ff to the command line.
So according to everyone who is supporting this thread, I should be fine with the following command assuming that all 4 individual disks have an identical 'fd' partition, correct? mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2 The above command is what I am running and I will try it again on my test machine just for the sake of resolving this. I DON NOT want the 4th disk to be a 'hot spare' but rather an expansion of the RAID5 array to allow for more disk space / redundancy. I think the 'mdadm' utility has a 'grow' option to do the same thing to an existing RAID system if I had only 3 drives to RAID5. Let me know if anyone sees an error in my command syntax and thanks again for all your help!
participants (5)
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Carlos Williams
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Dwight Schauer
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Jackson Alley
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Louis Brazeau
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Robert Howard