Synology DS410, Failing drive

[sketchpad]

Hi everyone,
We have a Synology DS410 at work, x3 500GB drives for total storage of 1GB, I'm guessing RAID 5?
One of the disks is failing however the log refers to Disk 3 being defective but SMART says its Disk 1 thats abnormal.
Which should I replace and is it as simple as just hot swapping in a new drive of same capacity?
Screenshots below.
Thanks in advance.

 

[Solandri]

You need to replace both disks. Disk 3 generated read errors so was dropped from the array. Consequently, your array no longer has redundancy (you can see Disk 3 is no longer part of Volume 1 in the second pic). A second disk failure will result in the loss of all your data. You need to replace Disk 3 ASAP and rebuild the array.

Disk 1 is reporting SMART errors. These indicate an increased chance of a future failure. They do not necessarily indicate the drive has already failed. So you will also need to replace Disk 1.

Given the precarious state you're in, if you don't have a backup of the data in your array, I would make one now, starting with the most important data first. Do this before replacing Disk 3. Since Disk 1 is reporting SMART errors, there's a chance it could fail after you've replaced Disk 3 but while the array is rebuilding. If that happens, all your data will be gone. Manually backing up the most important data first will guarantee you have a copy of the data which can't be lost if the rebuild fails.

Once you've backed up, you can replace Disk 3 and rebuild the array. Then you replace Disk 1, and rebuild the array again. Should another drive die during either of these rebuilds, you will lose all data, and the backup will be your only recourse.

 

[sketchpad]

Thanks Solandri, we'll backup now then get 3 new 1TB drives and swap and rebuild in the order of Disk 3, Disk 1 and finally Disk 2.