Cannot Enable Write Cache on Smart Array 6400

[Marco DV]

Hi, I manage a HP ProLiant DL380 G4 server connected to a MSA20 array trough an internal Smart Array 6400 controller.

Since some time, I have a problem with write speeds, which have gone terribly down.

When doing simple tests like "dd if=/dev/zero of=./testfile" I noticed that writing starts fast, but starts crawling as soon as the amount of data written reaches 800-900 MB, and then I get terrible transfer speeds between 5 and 20 MB/s.

The write cache batteries were old and needed replacement, so they have been replaced now - all four of them, two in the server and two in the array. But the problem remains.

I used ACU CLI and discovered that the cache on the 6400 controller is not enabled. Maybe it needs to be enabled again, after replacing batteries?

Anyway, I cannot find a way to enable it: the command returns an error telling that this operation is not possible with this configuration.

Instead I successfully enabled the cache on the MSA20, but it wasn't enough to fix the problem.

How can I enable the cache in the 6400? What am I missing?

The cache module should be present and correctly inserted, because all other status outputs are fine.

Any clues?

Thanks.

Marco

[Torsten.]

The 6400 in the server works as a pass-thru only, the 6400 inside the MSA does the work. Are the batteries already charged?

[Marco DV]

Hi Torsten,

yes, the batteries have been changed more than a week ago and are reported by ACU as being OK.

What else can I check? I also checked that "arrayaccelerator" (or whatever that option is called) is enabled on the three logical drives inside the MSA20.

I forgot to say that the firmware in the controller would need to be updated, as far as I recall it has version 2.68 and ACU recommends an update, the latest is 2.84 I think. But can this really affect performance, or maybe the cache capability? And why only now, not before?

Thank you very much.