QNAP Storage HDD Expansion


I have a question about my TS420 QNAP NAS system that the QNAP forum are so slow to answer and I cannot wait for weeks.

Recently, I have realized some capacity issues and have decided its time to upgrade my storage drives from 2TB to 4TB.

Currently, there are 4 x 2TB (Model # WDC WD20EFRX-68EUZN082.0) inside the NAS and it is configured as a RAID 5 storage array.

My question is, can I remove one HDD at a time using "hot swap" method and slotting in my new 4TB drives? Will the RAID rebuild itself without losing any data or causing any file corruptions?

Thanks in advance.
Laila JacksonAsked:
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andreasSystem AdminCommented:
Read this:


One bit error during resyncing on the remaining disks and your array is broken.

So its as @jmcg said very important you have a FULL backup of all yout files on the NAS elsewhere.

also 4 times resyncing will stress the disks quite a lot and if you got a bad new one it might fail during resync, also result in data loss.

Its quite risky but it might work.

Here are the instructions for qnap NAS how to extend capacity online.


You should exactly follow this and NOT JUST pull one disk and plug a larger one and repeat.
The QNAP is advertised to work that way, but I never tried it myself. You'd still want a solid "before" backup and you'll need to be able to see the progress on the RAID rebuild so as not to put the next disk in too early. And I'm also not sure how automatically the new space will be made available once all the drives have been upgraded.
Laila JacksonAuthor Commented:
Thanks heaps. All worked fine.
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