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Upgrading Raid 5 to larger disks

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Posts: 7
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I have a 6x 4TB Raid 5 array in 2x OWC Thunderbay 4's. I've used 14TB of the 20TB available. Figure I shouldn't go over 15TB (75%), correct? Drives have about 17k hrs, HGST enterprise class.


So I'm thinking to 'upgrade' the array to 6TB or 8TB drives sometime in the near future. Prefer to keep Raid 5 for its speed.


I don't have enough drive bays to just add a second 6 drive array and transfer. What's the best practice?


Clone each drive one at a time with CCC? Or just replace drives one at a time and let it 'rebuild'?? I guess I could just use my individual backup drives (non-raid) to move the data.


Second question - I've just read that I should 'Validate' my array in Softraid regularly. I didn't realize and have run it for 6 years and never validated. Kind of scared to do so now if it means it'll need to rewrite tons of data. Any advice?






27" 5k iMac late-2014

OSX Yosemite

Softraid 5.8.4

2x OWC Thunderbay 4

6x 4TB Raid 5

Posted : 16/04/2021 10:48 pm
Posts: 7517
Member Admin

I think 85% is OK on a volume. (I don't know what the optimal limit is on APFS, I guess users will find out over time!)

Validate is safe. All it does is check adn update any parity blocks. There will probably be no updates until the last 20% or so of the volume. Validate does not touch your data.

Disk Warrior is the best way to protect your volume against volume directory damage, if you want to run a maintenance app.


To your question:

You can replace one disk at a time. Use "remove disk", then initialize and "Add disk". When all 4 are replaced,  you can "resize volume" to expand the volume size, and use the additional space available.

Posted : 17/04/2021 2:53 am
Posts: 1
New Member

Sorry to resurface an old thread. I have 4, 4TB drives in a Thunderbay with RAID5. Am I correct in understanding that I can remove and then add larger disks, but not add more disks to the array? If I bought a second Thunderbay in the future for example, I'd have to destroy and recreate the array to add 4 new drives?

Posted : 19/03/2022 10:28 pm
Posts: 7517
Member Admin


Yes you would. Although I would keep the RAID as is and create a second RAID volume on the new enclosure. Easier to manage that way.

Posted : 20/03/2022 12:39 am