Software Raid Questions
Software Raid Questions
Hello.
We are running a Linux Raid 1 built during the install of Centos 7. At this time the /dev/sdb drive in the raid failed.
What we have done is replace the drive and its showing at /dev/sdb using fdisk -l
I want to make sure I do this rebuild correct. Currently we have 3 raid volumes dm0 / dm1 / dm2 which are the /boot, / folder and swap. The problem is to rebuild the raid I guess I need to duplicate the partitions on /dev/sda1, /dev/sda2, /dev/sda3 on the /dev/sdb drive. Is there first of all a correct way to do this? Am I also doing this in the correct method.
Then my guess is that I need to resync the raid which I would like to confirm the correct commands for but does look more simple.
Anyway I guess I want to make sure and get this correct first time before I make any mistakes or loose any data.
Any help would be great.
Thanks.
We are running a Linux Raid 1 built during the install of Centos 7. At this time the /dev/sdb drive in the raid failed.
What we have done is replace the drive and its showing at /dev/sdb using fdisk -l
I want to make sure I do this rebuild correct. Currently we have 3 raid volumes dm0 / dm1 / dm2 which are the /boot, / folder and swap. The problem is to rebuild the raid I guess I need to duplicate the partitions on /dev/sda1, /dev/sda2, /dev/sda3 on the /dev/sdb drive. Is there first of all a correct way to do this? Am I also doing this in the correct method.
Then my guess is that I need to resync the raid which I would like to confirm the correct commands for but does look more simple.
Anyway I guess I want to make sure and get this correct first time before I make any mistakes or loose any data.
Any help would be great.
Thanks.
Re: Software Raid Questions
Show the contents of /proc/mdstat so we can see how it looks now.
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Re: Software Raid Questions
Hello.
The output is:
Also if this helps:
Thanks,
Paul.
The output is:
Code: Select all
root@server [~]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda2[0]
511936 blocks super 1.0 [2/1] [U_]
md2 : active raid1 sda3[0]
451429376 blocks super 1.1 [2/1] [U_]
bitmap: 4/4 pages [16KB], 65536KB chunk
md1 : active raid1 sda1[0]
16760832 blocks super 1.1 [2/1] [U_]
unused devices: <none>
root@server [~]#
Code: Select all
root@server [~]# fdisk -l
Disk /dev/sda: 480.1 GB, 480103981056 bytes
255 heads, 63 sectors/track, 58369 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b596e
Device Boot Start End Blocks Id System
/dev/sda1 1 2089 16777216 fd Linux raid autodetect
/dev/sda2 * 2089 2153 512000 fd Linux raid autodetect
/dev/sda3 2153 58370 451560448 fd Linux raid autodetect
Disk /dev/md1: 17.2 GB, 17163091968 bytes
2 heads, 4 sectors/track, 4190208 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/md2: 462.3 GB, 462263681024 bytes
2 heads, 4 sectors/track, 112857344 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/md0: 524 MB, 524222464 bytes
2 heads, 4 sectors/track, 127984 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdb: 480.1 GB, 480103981056 bytes
255 heads, 63 sectors/track, 58369 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
root@server [~]#
Paul.
Re: Software Raid Questions
So you'll want to duplicate the exact layout of your current partition of /dev/sda on the new disk (I presume /dev/sdb). You can do that with sfdisk by listing sda and piping it into sfdisk run against sdb but you can also do it manually if you prefer. I would make sure that if you use fdisk you put it in sector mode and print the current start positions on the partitions on sda so you can create them on the exact same sector on the new disk. Once that's done - it may require a reboot to take effect but if the disk is otherwise unused then it should take effect immediately - then you can use mdadm --add /dev/mdX /dev/sdbY to add each of the new partitions to the md0-2 arrays, one at a time then let each one finish before you start on the next. Make sure you add the correct partition to the correct mdX.
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Re: Software Raid Questions
Hello.
The new drive is /dev/sdb and the original /dev/sda so your assumption is correct.
I have not used sfdisk much before so do you have some example commands which you would use to do what I need to do?
The raid commands were as I expected but its the partition part which I have never done before.
Thanks,
Paul.
The new drive is /dev/sdb and the original /dev/sda so your assumption is correct.
I have not used sfdisk much before so do you have some example commands which you would use to do what I need to do?
The raid commands were as I expected but its the partition part which I have never done before.
Thanks,
Paul.
Re: Software Raid Questions
Never had to do it myself but google finds a raft of hits using "sfdisk clone partition table". Read a few, use the one that makes the most sense!
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Re: Software Raid Questions
Hello.
I have figured it out, easy in the end:
sfdisk -d /dev/sda > part_table
then:
sfdisk /dev/sdb --force < part_table
Thanks,
Paul.
I have figured it out, easy in the end:
sfdisk -d /dev/sda > part_table
then:
sfdisk /dev/sdb --force < part_table
Thanks,
Paul.
Re: Software Raid Questions
Hi.
So that anyone else reading this post might run into this situation I have written a guide to help people:
https://www.ukhost4u.com/blog/replacing ... nd-sfdisk/
Any feedback I will be happy to include. Also thanks to: TrevorH
Paul.
So that anyone else reading this post might run into this situation I have written a guide to help people:
https://www.ukhost4u.com/blog/replacing ... nd-sfdisk/
Any feedback I will be happy to include. Also thanks to: TrevorH
Paul.