Buying replacement drive for zfs raidz1 array - Unable to find similar disk in Country

I currently have an old array of 6x 3TB WD WD30EFRX CMR drives used for backups of VM images.

over the years I had one drive fail so I put my cold spare in production (bought 7 disks at the time)

now I have another failed drive and I am unable to source an identical drive in my country. I also cannot source its replacement, the 3TB WD30EFZX. I am not going to buy an SMR drive with ZFS.

My question is should I:

  1. get a WD40EFZX or WD40EFPX 4TB Drive (understanding I can only use 3TB of space on it)
  2. get a Seagate Ironwolf ST3000VN006 ( I hope its not 1Mb smaller in disk allocation, will that cause a problem)
  3. Do I buy two larger drives (18 or 20TB) to setup as mirror and replace the array.

Safest would of course be option 3 given the age of the 3TB drives.

Option 1 works, is also certainly cheaper and avoid that potential risk listed in option 2.

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Any of those alternatives should work. If it was me, I would go with #3, but obviously that’s more expensive up front.

As for #2, if you hand out entire drives to ZFS it should leave a little bit of unallocated buffer area at the end for just the reason that replacements might be a tad smaller. Check the partition table of your drives to be sure.

E.g. here’s the partition table of one of my ZFS drives:

            1007.0 KiB  free space
   1        12.7 TiB    Solaris /usr & Mac ZFS    zfs-1b94a36dxxxxxxxx
   9        8.0 MiB     Solaris Reserved 1
            1007.5 KiB  free space

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From amazon usa - not sure if shipping to your country is an option. Amazon.com: Western Digital 3TB WD Red Plus NAS Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, CMR, 64 MB Cache, 3.5" - WD30EFRX : Electronics

You’re asking multiple questions here at once, so let me try to knock em all out:

  1. no matter what, your array needs to be healthy as quickly as possible

  2. I would get n+1 of the drives you plans to use for your new array

  3. insert new drive destined to be backup of new array into old array and rebuild

  4. build new array and transfer

  5. reclaim new drive from old array and add to new array as hot spare (or cold spare)

  6. don’t forget your throughput will suffer going from more drives to fewer.