Upgrading Mirrors t...
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Upgrading Mirrors to Larger Drives

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I am running a Mac with a 4-bay Mercury Quad Pro enclosure with two sets of mirrored drives, an 8TB set and a 4TB set. My 8TB mirror is full and I need to upgrade to larger drives (which will be a 14TB set), and I'm wondering what the safest/best way to do that would be. Can I just pull out one of the 8TB drives and re-mirror the remaining drive to the new 14TB drive, then swap out the remaining 8TB for the other new 14TB and re-mirror again? Or should I just pull out the 4TB set, put in both new 14TB dives in those bays, create a new volume, and copy the 8TB volume to the new 14TB volume? Will my 4TB volume be intact if I temporarily remove the drives from the enclosure then just put them back in?

I have seen other threads mentioning "certifying" drives before creating volumes, but I can't really find much in the way of documentation about what that means or the details of that process. And since all of my enclosure bays are full, I'm not clear on how I would "certify" a new drive without breaking my existing volume(s). 

Any clarity or suggestions would be appreciated!

This topic was modified 1 month ago 2 times by unusualmuse
Topic starter Posted : 16/10/2022 1:32 pm
Member Admin

There are two ways.

replace the drives one by one and resize the volume. (This has the limitation that resize requires a version of SoftRAID that can run in Big Sur or older, like 6.0.5. there is a bug that prevents resizing in 6.2-6.3)

remove one disk, insert a new one, create a volume, copy the data, then "convert" to Mirror". This only works on HFS volumes, which you are probably using.


Certification is something you do to new disks. It takes about a day per 2TB, but it tests the entire disk for reliability, as disks are sold untested, so this reduces early failures and "DOA" drives.

Posted : 16/10/2022 5:13 pm