Inserting a SATA drive into a “hot swap” tray causes a momentary problem that leads the Intel RST RAID 10 array to begin rebuilding. The first message from Intel begins like this:

SATA array disk: Removed.
Volume FS_RAID10_A: Degraded. 
Volume FS_RAID10_B: No longer present on system.
Volume FS_RAID10_B: Detected.

On one occasion one of the volumes was at this point flagged as having 23 parity errors; the other had none.

The OS is Window 7, and the freeware program HotSwap! is installed so the drive can be easily removed later. It’s resident, but it's not clear that it is involved upon drive insertion. (On XP I need to invoke it when I insert a drive, else the OS won't see it, but that's not the case with Window 7.)

What there is of common wisdom on the subject holds that it’s a power supply problem, and powering the drive from a different cable will be the solution. I’ll try that, but if the system were that glitch-sensitive people with similar loading would be seeing it every time a drive (or array of drives) woke from napping.

The RAID array is serviced by the Intel hardware on the motherboard; the drive being swapped connects to the other RAID controller on the motherboard. The hot-swap tray is passive and just passes the SATA connections through.

Thoughts from anybody with specific knowledge about what's happening?

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    So what is the expected behavior as you understand it? To my knowledge when you insert a new drive in a RAID array, it rebuilds itself so what you see is expected behavior. And part of the rebuild process is to check integrity of the existing drives in an array. – JakeGould Aug 20 '16 at 21:31
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    Adding to what @JakeGould wrote, is the drive you are hotplugging part of the RAID array or not? – a CVn Aug 20 '16 at 21:37

Thoughts from anybody with specific knowledge about what’s happening?

Yes. This is all expected behavior. When you insert a new hard drive into a RAID array of any kind, the system will “rebuild” the RAID to utilize the new drive in the array. And part of the rebuild process is to check the integrity of all drives in the array itself. So one of your drives was “degraded” it simply means it’s dying or slowly dying.

But that all said, many RAID systems use different terminology for different events. In your case it seems “degraded” means one disk member of an array is failing, but in my experience a “degraded” state on a RAID array means the whole RAID array itself is degraded.

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