Topic: RAID Recovery And Drives That Are Not Exact

[rick1908]

I had two Western Digital 300 GB PATA drives installed on a box that was upgraded from verion 6 to version 7 final.

One of the drives went down and need to be replaced. I could not find an exact copy of drive that went down and had to go with a Maxtor 300 GB drive. Seems CompUSA only carries one 300 GB PATA drive and nothing larger than 300 GB.

I followed the how-to's:

http://mirror.contribs.org/smeserver/contribs/mblotwijk/HowToGuides/AddExtraHardDisk.htm


http://mirror.contribs.org/smeserver/contribs/jbennett/howto/Recoving%20From%20Raid%201%20Failure.htm

however the drive geometries are not the same. The good drive is set up like this:

Disk /dev/hdc: 300.0 GB, 300069052416 bytes
16 heads, 63 sectors/track, 581421 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdc1   *           1         203      102280+  fd  Linux raid autodetect
/dev/hdc2             204      580902   292672296   fd  Linux raid autodetect
/dev/hdc3          580903      581420      261072   fd  Linux raid autodetect

I set the new drive up like this:

Disk /dev/hda: 300.0 GB, 300090728448 bytes
255 heads, 63 sectors/track, 36483 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hda1   *           1          13      104391   fd  Linux raid autodetect
/dev/hda2              14       36451   292688235   fd  Linux raid autodetect
/dev/hda3           36452       36483      257040   fd  Linux raid autodetect

I am having troble with this command:

raidhotadd /dev/md2 /dev/hda3

I get the following answer:

/dev/md2: can not hot-add disk: too small disk!

I am guessing I made the wrong choices on the Start and End cylinders when partitioning the new drive. Is there a work around?

a. a better partition setup on the new drive
b. a way to reduce the size of the /dev/hdc3 partition (the good drive) so that it raidhotadd with the new drive
c. any other suggestions

Thanks for your help.

One other thing, I have added the /dev/hda1(2) partions to the raid already. Does anyone know the commands to remove them from the raid so I can repartition and then 'raidhotadd' them again?

Sincerely,
Rick Evans
Ft. Lauderdale, FL

[Gaston94]

Hi,
I cannot really argue about it, but I would not try keeping a RAID system with different disks geometry.

Considering the fact that when one disk fail, you might foresee some issue with the other one, I would rather go that way :
 - purchase two identical disks
 - create a raid array on this disks
 - copy data from remaining (old)disk to the new raid array
 - adjust mbr settings for booting on the correct array
 - stop the raid on the old disk

You can keep your "old" disk in your server for extra usage (like hot backup)

One other thing, I have added the /dev/hda1(2) partions to the raid already. Does anyone know the commands to remove them from the raid so I can repartition and then 'raidhotadd' them again?

just set the device faulty and remove them from the raid array:

Code: [Select]

mdadm --manage /dev/md1 --fail /dev/hda1
mdadm --manage /dev/md1 --remove /dev/hda1

G.

PS : I do not understand, you first write

a box that was upgraded from verion 6 to version 7 final.

and then

raidhotadd /dev/md2 /dev/hda3

and it cannot be   SME7 is using mdam tools

Nevertheless, with raidtools, the command should be

Code: [Select]

raidsetfaulty /dev/md1 /dev/hda1
raidhotremove /dev/md1 /dev/hda1

PS2 if you are not familiar with above operations, I would recommand you try the operation on a test system. VMWare installation sounds good to me for this purpose too

[rick1908]

My head is swimming...

...This looks a weekend project that might take part of the week as well.

In the mean time...I am raiding the partition with all the pertinant data, I have nightly backups, as nightly well as remote rsync backups. I am feeling pretty bulletproof.

This may be the time to consider a backup and fresh install of SME 7.0.

Thank you so much for the help.

Rick Evans
Ft. Lauderdale, FL