Can i convert a mdadm from raid 6 to raid 0

Choakem used Ask the Experts™
Can i convert a mdadm from raid 6 to raid 0

I have a machine with 10&10TB of data in raid 6.

I'm looking to convert to Raid 0

I dont really care if I lose the data (I have several copies) I just would prefer daving the time off wiping machine - raid 0 - then transferring it all back again.

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdc1[2] sdi1[8] sdf1[5] sdj1[9] sdh1[7] sde1[4] sdg1[6] sdd1[3] sdb1[1] sda1[0]
      4190208 blocks super 1.2 [10/10] [UUUUUUUUUU]

md1 : active raid1 sdc2[2] sdi2[8] sde2[4] sdj2[9] sdg2[6] sdf2[5] sdh2[7] sdd2[3] sdb2[1] sda2[0]
      523712 blocks super 1.2 [10/10] [UUUUUUUUUU]

md3 : active raid6 sdc4[2] sdj4[9] sdi4[8] sde4[4] sdf4[5] sdg4[6] sdh4[7] sdd4[3] sdb4[1] sda4[0]
      75980845056 blocks super 1.2 level 6, 512k chunk, algorithm 2 [10/10] [UUUUUUUUUU]
      bitmap: 2/71 pages [8KB], 65536KB chunk

md2 : active raid6 sdc3[2] sdg3[6] sde3[4] sdi3[8] sdf3[5] sdj3[9] sdh3[7] sdd3[3] sdb3[1] sda3[0]
      2110783488 blocks super 1.2 level 6, 512k chunk, algorithm 2 [10/10] [UUUUUUUUUU]
      bitmap: 2/2 pages [8KB], 65536KB chunk
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Top Expert 2016
nociSoftware Engineer
Distinguished Expert 2018
Any error on any device will kill the the complete array in RAID 0.
So you may find it becoming a problem to restore data at periods of devices fail faster then you can do restores.
Reason raid6 is prefered above raid 5 is the number of  arrays that ended in complete failure during recovery of the data, where different drives after the initial one failed.

Also consider pushing 10TB takes some time. During that time there is no array that is usable.
Can you afford the down time? not just the loss of data?
David FavorFractional CTO
Distinguished Expert 2018

1) Make a backup before you do this.

2) Check backup logs carefully to ensure the backup was correct. (You'd be surprised how many backups contain errors.)

3) Connect your RAID array to a UPS.

4) Test the UPS by unplugging it to ensure high battery life. (You'e be surprised how many people never deplete UPS batteries, so over the years battery life will drop dramatically.)

5) At this point you can run your conversion...

As noci said, there's a good chance this type of conversion will destroy your RAID array, so better to just reformat the array as RAID 0 + restore a backup.

Keep in mind RAID 0 is JBOD (just a big old disk), so the resulting RAID array will have no RAID quality... no data redundancy...
Even if the conversion worked, it would be both error prone and likely longer than resyncing with another copy. Unless you network is really slow or other copies are hosted on remote locations over slow links
You may consider the zfs variant of raid 0. if you have a small dataset than can be moved to 2 drives, you can throw all your data on 2 existing drives, and then add the other drives.


sorry for not replying - I bit the bullet and wiped and made a fresh copy - thx all.


Thanks all - Not the answer I want but the answer I expected :P

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