P400 with BBWC AND physical disk write cache

[Daniel Gilanyi]

Dear all,
after installing the battery kit on a P400 controller, could I get some extra performance if I also enable the Physical Disk Write Cache option in the controller utility? (It is disabled by default and I know it's not battery backed up but the power supply is redundant, so maybe it worth the risk if only the performance counts...)
thx!

[TTr]

At one point you say "after installing the battery kit" and at another "I know it's not battery backed up". Which is it?

If you don't have the BBWC you already know the risk. At the same time the array might not enable the write cache if it senses that the BBWC is not installed.

[Daniel Gilanyi]

As I know the battery kit is for the controller (card)'s cache memory (256m in my case) but there is also a smaller local cache in the disks, which can be enabled/disabled from the config utility.
It seems these are disabled by default.

[Patrick Terlisten]

Hello Daniel,

there are two parts: You can add cache memory to the controller, and you can add a BBWC (a batterey module for the cache) to the controller.

What kind of extension did you add? Only cache or cache and BBWC?

Yes, you can get a little more performance if you enable the physical drive cache, but I wouldn't do it. This cache isn't battery backuped, so you can lose data, if the server crahs and unwritten write IOs are in this cache.

Best regards,
Patrick