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Ouze

[SOLVED] Adding new drives to the array while multiple drives preclear, yay or nay? Unraid 6.4.0

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Hello all,

I upgraded a bunch of drives around my house, so I took the known good all drives and added them to my server; a 4/6/8TB drive. I noticed you can preclear multiple drives simultaneously, so I did exactly that, and as expected, the 4TB is clear, the 6TB is almost clear, and the 8TB (which I only sort of trust) has a way to go in the first of two cycles. 

 

My guess is that I don't have to wait for that 8tb to finish clearing to monkey with the array, right? Specifically, I have a super old 1tb drive that I want to drop from the array and slot in the 4 or 6 and rebuild. I bet I can do that while that other preclear continues running. 

 

Is it wise, though? Should I wait for all that 8tb preclear action to finish before I start doing other stuff? Or does it not matter? I want to find the right balance between saving time, and being safe. 

 

Thanks!

Edited by Ouze
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You really should upgrade your Unraid and possibly the preclear plugin if it isn't the latest, but since you are already going...

 

While technically it should be possible, I would wait until all preclears finish to make any changes to your disk assignments in case anything goes wrong. However, I would question whether there is even any need to preclear.

 

The only scenario in which Unraid requires a clear disk is when ADDing it to a NEW data slot in an array that already has valid parity. This is so parity will remain valid since a clear disk (all zeros) has no impact on existing parity.

 

When Unraid does require a clear disk (only that one scenario), it will clear the disk when you add it to the array if it isn't already clear. Older versions of Unraid would take the array offline to clear a disk, and so preclear was born.

 

Since Unraid now will clear a disk without taking the array offline when it requires a clear disk (only that one scenario) the only purpose of preclear is to test a disk. People sometimes even do multiple preclears on a new disk in order to "burn it in" to try to get it past the stage of "infant mortality". Like many electronics, if it doesn't fail early it might last until obsolete.

 

So, if these weren't new disks and they are in good health according to their SMART attributes, then I would say there is no good reason to preclear them. Not even for that one scenario where Unraid requires a clear disk since it will do it anyway. And of course, it doesn't need a clear disk for your scenario (replacement).

 

 

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Thank you for the swift response, and oh boy, I didn't realize I was so behind on updating the Unraid OS :/ 

 

 

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Just so you aren't confused by my mention of upgrading and how it relates to preclear. It doesn't. Everything I said applies to the version you have, including the fact that Unraid doesn't take the array offline when clearing a disk. So you could just stop the preclears if you want and get on with using those disks if they are healthy.

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In fact, everything I said about clearing also applies to older versions of Unraid. But on early V6 and before Unraid would take the array offline if it needed to clear a disk (only for that one scenario).

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I get that, thanks. I still want that long running preclear to re-run because I'm not 100% sure it's good; it had a reallocated sector. Maybe it was just that one, and it's totally fine, but in my limited experience one reallocated sector tends to turn into more and I want to stress it a bit more first.  Also, those two disks will go into new data slots.

 

Mostly I was surprised by how out of date I let my unraid become. 

 

 

Edited by Ouze

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