EX2 Ultra NAS - RAID1 - procedure to replace one disk

I have a My Cloud EX2 Ultra NAS, and just recently a red light has come on indicating a disk problem. The dashboard is telling me one of the disks is bad and that I should replace it. OK - I got the unit in 2018, so it’s coming up on 6 years old.

I currently have two 6 TB disks in it, arranged in a RAID1 array. I would like to just replace the current bad disk with another Western Digital Red 6 TB disk - but WD doesn’t seem to sell these online (currently, UK) and I can’t find any for sale directly from Amazon either. (There are third-party sellers on Amazon - but I don’t like to buy from a seller I don’t know/trust.) Is this just a temporary issue that they’re out of stock, or should I be looking at other solutions?

I obviously haven’t done this before. How precise do I need to be about replacing the bad disk with one of exactly the same size? I mean, does the new disk have to have exactly the same number of bits? If it’s not critical, then it makes me wonder… what would happen if I just whacked an 8 TB disk in there? Would the NAS just behave as if there is 6 TB of user storage and it would ignore the excess storage in the higher capacity disk?

If the NAS would accept one 8 TB disk, then what would happen if I later replaced the other disk with a second 8 TB disk? Would I then just immediately have a NAS with 8 TB of apparent storage, arranged in a RAID1 array?

Also, any particular tips I should be aware of before changing the disk? Is it just a matter of powering down the NAS and following the instructions to remove/replace the disk? Will the NAS immediately realise that one of the disks is blank and all the data needs to be duplicated across to it? Will it complain? I assume this is pretty standard for a NAS, but I just don’t have any experience doing this. Do I need to “warn” the NAS in advance somehow that I’m about to replace a disk?

1 Like
  1. Backup all data to ANOTHER device. Do that first. With one failed disk. . . you are at risk of data loss.

  2. You need to take a look at the S.M.A.R.T stats to see if the disk is really bad. Diagnostics inherent in OS/5 software is sub-par. Look for utilities from a user named Cerebus.

  3. Swapping disks is plug and play. Should be very easy. If you put in a larger disk; it will only use the same space as the smaller disk. The “copy” of data from old disk to new disk should be automatic (I think) If you (down the road) put in a larger disk. . .you should get an “expand” option in the Volume setup menu of the dashboard after the copy is complete.

  4. DO NOT buy a WD Red drive; unless you can directly verify it is a CMR type and not SMR. Despite advertising; SMR is not fit for NAS (or any other) service. My thinking is that a spec sheet doesn’t tell you the drive is CMR - - - presume it is SMR and not fit for service. (Certain popular WD Red drives are SMR)

The WD Red Plus series and WD Red Pro series were (last I checked) exclusively CMR drives.
You are not restricted to WD drives in this NAS.

All WD 8 TB and above are CMR. They are now labelled WD Red Plus drives.

Hi @osullic im in the same situation did you manage to get the job done? what disc did you get. thanks

Hi there,
If you just have to replace one disk, then I think the process should be pretty straightforward - I found another very helpful thread here on the WD Community walking through the process of upsizing the disks:

One thing I was considering was just upsizing one of the disks for now, and upsizing the second disk later - something which WD support (seems incorrectly) told me wasn’t possible - but I think this is indeed possible by following through the steps in that other thread I just linked to.

However, in my case things became a little more complicated as I had 2 disks both (suspiciously) fail within weeks of each other. Well, not quite fail, but the NAS was showing red lights and warning me that the disks needed to be changed. While I already had separate backups anyway, the disks were still good enough to read all data off them onto a temporary portable HDD, and then I just put 2 brand new WD Red 6TB disks into my enclosure and started from scratch, so to speak.

I’m going to investigate the SMART data on the “bad” disks, and if suitable, I might resell them - with full disclosure of course.