Upgrade - replace with larger HDD, in RAID6, two at a time?

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cpu8088 wrote:

you answered your question already

 

 

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Really, which one?

That technically a RAID6 can survive two lost discs? So it should rebuild both when replaced.

That doing such may or may not be faster than doing them sequentially?

Or perhaps you are referring to exposure to a single disc failure?

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Hopchen wrote:

Even then, the NAS will still only sync one disk at a time as far as I am aware. 

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OK, thank you for attempting to answer one of the questions.

I should, perhaps, been more informative.

I have a Computer Science background & have decades of experience in the industry.

I HAVE BACKUPS. I have generally stopped updates (where I dont' they are minor & I backup again).

I am upgrading capacity.

I have done 2 of 6 drives.

Each drive, due to background priority, takes around 24 hours to resync.

I would prefer to get this over and done with.

ON the basis of MTBF, I suspect a reasonably low chance of a failure in the next few days. If not I can recover.

I had presumed that someone, particularly Netgear themselves, would have experience with a 2 drive RAID6 failure/resync scenario.

(where I would expect a resync - after shutdown/replace 2 drives/reboot - would actually resilver both in one go, that's how I would have designed it)

(I would expect the parallel IO to allow faster resync, than two sequential ones)

So I asked a couple of questions to confirm my thoughts.

So thank you for your concerns.

Should anyone have actual knowledge of the answers, I would be thankful for the input to my decision making process.

Oh well, seeing I'm awaiting delivery of the rest of the drives I may as well test it.

I have expanded more than one added drive at a time by disabling XRAID, selecting the drives, and selecting "Expand".  It definately took less time than one at a time.  But I don't know what you could select for replacement of two drives.  Just trying it sounds like a plan.  If nothing else, it should do one then the other.  If you don't disable XRAID first, then put the drives in with power off so it sees them at the same time.  If you put them in with power on, it will see the first and start re-sync before you get the second in.  When replacing drives, it might even start with the first one if XRAID is disabled and power is on.

Let us know what you find out.