Hi,
I was trying to grow my raid5 array to raid6 with one more disk. And I
was wondering about when would the backup take place and when would
the backup file is required (or not required).
And I found this thread "Re: Backup file size when migrating from
raid5 to raid6?"
two steps were mentioned in the thread to reduce the time of level changing.
so I followed the steps,
currently there were 3 disks in my array.
$ mdadm --grow /dev/md0 --level=6 --layout=preserve
mdadm: Need 1 spare to avoid degraded array, and only have 0.
Use --force to over-ride this check.
$ mdadm --grow /dev/md0 --level=6 --layout=preserve --force
mdadm: level of /dev/md119 changed to raid6
the array became raid6 and the state is clean, degraded and nothing
more happened, I thought it would create Q in this step, but there
were no writing from iostat.
so I added one disk
$ mdadm --grow /dev/md0 --raid-devices=4 --layout=normalise
State : clean, degraded, reshaping
but from previous post in this thread, I thought the backup file is a
must under this circumstance, and according to the throughput of those
disks (not slow), there seemed no backup was happening.
my question is,
1. "mdadm --grow /dev/md0 --level=6 --layout=preserve" will this
command create Q even though it degrades the array?
2. Is backup happening in second step (reshaping)? if it's happening,
why don't I need a backup file?
Thanks,
