I've a recently upgraded 3PAR array ( 3.2.1 MU1) , which overnight is getting some high iowaits – to the point where some paths to drop and servers to crash (particularly noticeable with e.g. Oracle). I think since the upgrade, but I'm not 100% sure.
When we look at 'total disk' chart on the 3PAR management tool (SSMC) we see that at 0100 BST service time shoots up (6k ms) and indicates that there are 8 near line disks that are on the same pair of nodes, all showing high service time.
This has happened several nights now – and it's different nodes and sets of disks each time – but not quite every night. It says in this state for a couple of hours.
Now this sounds like like some sort of scheduled task (media scrub maybe?) 'going off', but I'm at something of a loss to figure out what it might be. Is anyone able to point me in the right direction for how to figure out what's going on here?
Best Answer
I would suggest looking at what is running on the nearline drives. You will likely need to tune some of that to fast class.