Adding a drive to a raid array


I have a LSI 9260-8i HBA controller with a 3 drive RAID 6 configuration.  I'd like to add a 4th drive to it.  I've read the docs but am not sure how the controller behaves exactly.  Does it bring in the new drive in the background while the array is in use, or do you have to wait until the process is complete through the card's BIOS UI?  That could take a while with 3-4TB of data on the current set.


Ben ConnerCTO, SAS developerAsked:
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It does it hot.  You experience a performance hit, but only if you are pounding the array.  

Pre-upgrade hints
 - UPDATE firmware of controller and HDDs, if necessary first, then power cycle the computer (if controller firmware and/or drivers were updated, otherwise unnecessary)
 - Make sure you have the right disk drive.  Ideally same make/model, and absolutely don't use some consumer class $59.95 drive not designed for 24x7x365.   You need server/enterprise class with that controller.
 - Always do full backup first.   Reason is expanding array will read every block of every drive, some blocks wouldn't have been touched since the day the RAID was initially built, so you could have a bunch of unreadable blocks that would have escaped detection.  Last thing you want is drive failure(s) during an upgrade, as that will cost thousands and thousands of dollars from recovery lab. --> But risk is really, really low going from a 3-disk RAID6 to 4-disk RAID6.

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Ben ConnerCTO, SAS developerAuthor Commented:
Good advice.  These are the HGST HE8 8TB drives, so not the stuff from Best Buy.  

Have been struggling to get a darn flash drive bootable so I can do a firmware upgrade.  It is indeed behind on that.  

Given the load I typically see I don't think performance would be an issue.

So I add the drive into the array and I can then reboot the server and it will continue rebuilding it with the new drive?  (vSphere 6.0 environment)

Those are wrong drives for that controller.  You want a native 512 byte drive.  The HE8s come in 512e and 4kn.    (Meaning that drive actually does 4k I/O internally, and emulates a 512 byte drive with read/modify/writes..     Unless EVERY I/O is not only a multiple of 4KB, but it is aligned to block number that is a multiple of 4KB, then you will take a performance hit, AND in event you are rebuilding then you risk data loss.

That ancient controller can't deal with 4KB sectored drives either, so if you got one of them, then it just won't work.
Ben ConnerCTO, SAS developerAuthor Commented:
Rats.  Even with updated firmware?
Which in that line would you suggest?
I thought the 512e indicates (e)mulation mode that would be compatible with older controllers.  ?

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