HP-UX 11i triggers storage logical drive write policy to write through

[Gambiza]

HP-UX system triggers the storage system controllers to go into "Write Through" mode on the logical drives. We always have this issue when we run the performance tests or initiate I/O to the storage system. When we initiate the I/O initially, the controllers goes into write through mode on the logical drive. We have to manually set mode to write back on the logical drives everytime we initiate I/O. Therefore causing a huge drop in performance on our applications. Upon the manually enabling "write back" on the storage controller the performance is superb. Unfortunately we have to do this very often to sustain the performance needs of our applications.

We only experience this with the HP-UX systems all 10 of them. We have Linux systems in our configuration and we don't run into this issue.

Is there something we can "tweak" or set to avoid this?

Thanks in advance,

-Tad