Re: Replacing all disks in a an array as a preventative measure before failing.

On Wed, 9 Feb 2022 07:02:45 -0600
Roger Heflin [off-list ref] wrote:

On Wed, Feb 9, 2022 at 3:12 AM Red Wil [off-list ref] wrote:

quoted

Hello,

It started as the subject said:
 - goal was to replace all 10 disks in a R6
 - context and perceived constraints
   - soft raid (no imsm and or ddl containers)
   - multiple disk partition. partitions across 10 disks formed R6
   - downtime not an issue
   - minimize the number of commands
   - minimize disks stress
   - reduce the time spent with this process
   - difficult to add 10 spares at once in the rig
   - after a reshape/grow from 6 to 10 disks offset of data in raid
     members was all over the place from cca 10ksect to 200ksect

Approaches/solutions and critique
 1- add one by one a 'spare' and 'replace' raid member
  critique:
  - seem to me long and tedious process
  - cannot/will not run in parallel
 2- add all the spares at once and perform 'replace' on members
  critique
  - just tedious - lots of cli commands which can be prone to
mistakes. next ones assume I have all the 'spares' in the rig
 3- create new arrays on spares, fresh fs and copy data.
 4- dd/ddrescue copy each drive to a new one. Advantage can be done
one by one or in parallel. less commands in the terminal.

In the end I decided I will use route (3).
 - flexibility on creation
 - copy only what I need
 - old array is a sort of backup
 

When I did mine I did a combination of 3 and 2.  I bought new disks
that were 2x the size of the devices in the original array, and
partitioned those new disks with partition the correct size for the
old array.  I used 2 of new disks to remove 2 disks that were not
behaving, and I used another new disk to replace a 3rd original device
that was behaving just fine.  I used the 3rd device I replaced to add
to the 3 new disk partitions and created a 4 disk raid6 (3 new + 1
old/replaced device) and rearranged a subset of files from the
original array to its own mount point on the new array.

Obviously, as usual in 'nix' world there are multiple solutions for
the same problem especially if you have a small number of drives.

My real question was regarding (4) if a exact copy bit-wise replica of
an entire disk/spindle would have any technical or safety concerns.

Thanks
Red