Can't replace faulty disk

[atiras]

I have an AS-604T running ADM 2.7.1 RFT5 and BIOS 1.11

It's configured as a single RAID5 volume (4 x 3TB) using Toshiba DT01ACA300 drives (compatibility should be OK).

Recently one of the disks (disk 4) showed a red light and was reported as "missing" in the Storage Manager. Data still accessible of course, but without redundancy so needs fixing. Log showed a sequence of media errors for that disk, followed by "There is a hardware error on the slot 4 disk". (Subsequently, removing and replugging this disk showed in the log, although obviously it didn't solve the hardware error; similarly, the system reports when other disks are removed and replugged).

I bought a new Western Digital Red 3TB disk (WD30EFRX so compatibility should be fine) -- I've always had a preference for WD but the NAS originally arrived pre-populated with Toshiba disks.

Took out the defunct disk, inserted the new disk. Green light now showing on that disk, so I was expecting it to resync over a long period and then the problem was solved.

Well, it didn't resync. The disk still shows as 'Missing"in the Storgae Manager (other disks are "Good"). The log doesn't report that the new disk has been plugged in. And if I go to Storage Manager > Volume 1 the Management button is greyed out.

What (if anything) am I doing wrong? What else should I check? I can try the new disk in another NAS but that holds got the data-backup for the first NAS and doesn;t have any spare slots, so I'm loathe to mess around with it as a first resort.

I'll raise a support ticket with Asustor as soon as I know I'm not being a total idiot!

[orion]

I guess WD30EFRX size is slightly smaller than Toshiba DT01ACA300. So NAS will not rebuild RAID-5 volume.
If you are familiar with linux command, gdisk, you can check total sector count on each disk. (example: gdisk -l /dev/sda)

The new disk size should be equal to or larger than original disk.

[atiras]

I can see that might be a ossibility -- I shall have to learn how to use the linux command.

However, does that explain why the disk is not seen at all? Shouldn't I be able to see it at least, and add it as a second volume? Or is the RAID5 configuration preventing that?

[orion]

I believe so (management button is grayed). Your RAID-5 volume occupies 4 disks. However you should be able to see the new disk under ADM web -> Storage Manager -> Disk. There should be 4 disks (with information: model name, temperature, ...).

[atiras]

Only three disks shown.

[atiras]

It may be the new disk is DOA -- another identical WD disk is now synchroning without a problem. It's a stopgap, as the disk now in use was pulled from another Asustor because it was reporting errors, but it has helped the diagnosis...

[atiras]

Yeah, the original replacement disk was faulty. New disk went in without any problem and has finished synching.