On 12/18/2011 12:51 PM, Sam Varshavchik wrote:
Jeffrey Ross writes:
It finally happened I had a disk failure in my RAID-1 system, I got a
message from SMART telling me that I had a drive failing and and
checked the mdstat and sure enough /dev/sda was missing/failed.
Ok, drive has been replaced and I did the following:
1) recreated the partition table with "sfdisk -d /dev/sdb | sfdisk
/dev/sda"
2) re-added the partitions back to the raid system (eg mdadm --add
/dev/md1 /dev/sda1 etc...)
3) recreated the boot sector on the new drive ***WAIT*** ran into an
issue....
The system was upgraded (via yum) from 14 to 15 to now 16 so I had
grub, not grub2 on the system, previously it was a simple
"grub-install /dev/sdX"
since grub has been replaced with grub2 I tried:
# grub2-install /dev/sda
/sbin/grub2-setup: warn: Your core.img is unusually large. It won't
fit in the embedding area..
/sbin/grub2-setup: error: embedding is not possible, but this is
required for cross-disk install.
so that didin't work, I'm doing something wrong, suggestions?
Carefully review the existing partition layout on what I presume is
your good disk, /dev/sdb, and compare it with your recreated partition
table on /dev/sda.
Hopefully, on /dev/sdb, your first partition starts on sector 2048,
and not sector 63. You probably partitioned your new /dev/sda with the
first partition starting on sector 63, which does not leave enough
room to install grub. You'll have to start over. Fail and drop all
your sda partitions on of all your md arrays. Create a new partition
table on sda, recreating the partitions exactly how they are on sdb,
starting with sector 2048, matching the start and the end of each
partition, on sda, exactly how they exist on sdb. Then you'll be able
to install grub.
If your sdb partitions start on sector 63, and you have no room to fit
them on sda starting at sector 2048, you'll have to recreate all but
your smallest partition on sda, then add and sync them to your array.
For the smallest partition, create it on sda making it as big as it
can be. Create a new md array for it on sda, with just one unit. I
believe you should be able to format it and mount it, even though its
degraded. Then you can manually copy over the contents from sdb, then
drop the array on sdb, and add its partition to the replacement md
array on sda.
Device Boot Start End Blocks Id System
/dev/sdb1 * 63 787184 393561 fd Linux raid
autodetect
/dev/sdb2 787185 16418429 7815622+ fd Linux raid
autodetect
/dev/sdb3 16418430 24418799 4000185 fd Linux raid
autodetect
/dev/sdb4 24418800 1953520064 964550632+ 5 Extended
/dev/sdb5 24418863 40050044 7815591 fd Linux raid
autodetect
/dev/sdb6 40050108 55665224 7807558+ fd Linux raid
autodetect
/dev/sdb7 55665288 1953520064 948927388+ fd Linux raid
autodetect
Bingo, mine start at 63, probably a hold over from previous installs.
ok, sdb1 is /boot, and I'm currently using 81 meg out of 372 meg and if
I'm doing my math right I should be able to easily shrink /boot by
another 1985 blocks (roughly 1MB) or so.
Based upon what you've given me, I suspect I can simply fail /dev/md1
(sda1 sdb1) resize it on the sda1 disk, copy everything across via cpio,
install the new bootloader on /dev/sda, once it comes up I can then
resize /dev/sdb1 re-add the partition to RAID and run the grub2-install
command.
Thanks,
Jeff
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