mirrored disks not showing same amount of activity

[Annelise Wilken]

Hello,

I have an rp4440 which has 28 external disks - these form 14 mirrored pairs across a split bus. The mirrored pairs are software mirrored across 2 controllers, when I look at the disk activity lights I expected to see the mirrored pairs light flashing at the same time - but it appears that only one "half" of the disks show consistent activity, the other "half" (mirror set) occasionally show some activity but not as much as the other set of disks - is this correct? Can anyone explain why this is so?

Many thanks.

[Ninad_1 · Accepted solution]

With software mirroring if you are saying Mirror-UX, then yes thats the behaviour expected - because with Mirror-UX you are mirroring the data, but there isnt any load balancing.
I cant remember, but I feel some product is capable of having this load balancing as well. Someone else probably would be able to point to that product.

Regards,
Ninad

[Steve Lewis]

Yes this is correct behaviour.
Read access goes to the first (primary) path in the volume group, unless that device is busy, in which case it reads from the alternate path.
Write access goes to both paths at the same time.

[Annelise Wilken]

Ok I get tha now - many thanks for the prompt replies - closing thread.

Thanks again.