On Wed, 3 Sep 2025 at 20:45 +0500, Roman Mamedov wrote: > If so, the safest would be to connect all three drives, and then: > > mdadm --add (new drive) > mdadm --grow -n3 (array) > mdadm --fail --remove (old drive). > mdadm --grow -n2 (array) I do something similar about once a year on my RAID5 array: I replace the oldest drive with a new one so each drive gets refreshed roughly every three years. The main difference is that I use mdadm’s "replace" feature, which keeps the array non-degraded while the data is copied: mdadm /dev/md0 --add-spare /dev/new_drive mdadm /dev/md0 --replace /dev/old_drive --with /dev/new_drive (not sure if this also works for other RAID levels) On my setup the copy takes about 8 hours. After it completes: mdadm /dev/md0 --remove /dev/old_drive This minimizes the time the array would otherwise run degraded and thus reduces the risk of a second failure during a rebuild. regards, Michael -- Michael Reinelt <michael@xxxxxxxxxxxxx> Ringsiedlung 75 A-8111 Gratwein-Straßengel +43 676 3079941
