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Converting raid 6 to raid 5

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I need more space, and I want to change my 4 6TB disks in raid 6 to 5. DSM wont let me do that. I found a tutorial in:

 

http://www.tjansson.dk/2013/09/migrate-from-raid-6-to-raid-5-with-mdadm/

 

that seems easy enough, using mdadm. The problem is that my synology system:

 

Captura%20de%20pantalla%202016-09-19%20a%20las%2022.14.45_zpsmbvbwbpf.png

 

is not just one raid 6 volume, but it has two additional raid 1 volumes, probably where the synology DSM lives. Now, the question: would the migration form raid 6 to 5 using mdadm destroy my files?. Would the DSM 5.2 still see the raid 5 disk?.

Edited by Guest

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It sounds like you do not have a backup of your files that you can restore. I would strongly caution you against converting to RAID5 without a backup. RAID6 without a backup is silly, RAID5 without a backup is dumb. That being said, perhaps the data is not that important and doesn't warrant a backup. In either case, there is not a good way to convert R6 to R5 in synology (probably because they know it is dumb :smile:).

 

Sorry.

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I do have a backup in amazon drive, but it would take a lot less time converting the array than downloading 10TB of data. I know there is no way in synology, but there is a way in linux. If you cannot help, then dont call me dumb. Please, dont help me. Not this way. :wink:

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I was not calling you dumb. I said running a Raid 5 without a backup would be really dumb. It sounds like you have a backup(?), but that it is difficult to pull the data back down.

 

Yes, the RAID 1 arrays are for the OS. I am not aware of any way you can boot to linux, modify the array, then reboot xpenology and have it magically work.

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My understanding with MDADM was that each array is separate and independent to the others, so converting your raid 6 array to a raid 5 array should leave MD0/1 intact as Raid 1s; these are effectively mirrors on each drive.

 

The question would remain however, what config file is written in DSM to record the array setup, or does it read from the array itself? I.e. changing from raid 6 to raid 5 (same as shrinking an array to remove a drive) be reflected in DSM or would it read from a file for what it has committed and therefore not reflect CLI changes.

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