Why "Resyncing started for Volume" after volume creation

[Zurd]

Brand new ReadyNAS RN214 with firmware latest firmware 6.91.

I did the formatting procedure of my 4 HDs by pushing the reset button, turning on the ReadyNAS and going into the boot menu for Factory Defaults.

But after that, if I create a new volume, the ReadyNAS always say "Resyncing started for Volume" and it takes almost 24 hours, I have 4 HDs of 4 TBs.

I'm wondering why it has to resync, the 4 drives are formatted, empty, clean, there is nothing on it. It's not even about X-RAID because before enabling it, it will start the resync.

The resync doesn't seem to affect performance but there's no data to sync.

[Sandshark]

Formatting and RAID sync are two entirely different things.  The sync has to create the superblocks, whether there is any data present or not.  Format prepares the individual drives and sync links them together.

[Zurd]

So it's a normal 24h operation for a RAID-5 with 4 HDs of 4 TBs?

I find it unexpected because my last NAS was a Drobo, there was no need to do any sync when doing a new RAID-5 volume.

[StephenB]

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@Zurd wrote:

So it's a normal 24h operation for a RAID-5 with 4 HDs of 4 TBs?

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Building a RAID-5 array requires computing all the parity blocks, and that needs to be done even if the volume is completely empty.  The process requires either reading or writing every disk sector in the array.

I'm not sure what you saw with the Drobo, but this applies to all NAS, not just ReadyNAS.