sync hangs

[Simon_G]

Greetings

I am running a sync command and it seems to take forever to complete and give back the prompt. The application complains slowness, i have cheked the box and there are lot of processes in "D" state from ps aux, so it looks like waiting on storage. My question is why sync takes such a long time to complete. Even if the sync completes and i run another sync in 5 minutes it takes the same time again. Env. RHEL 5.8 with HP EVA storage. I checked the max_sectors and it is the default of 512K, for EVA the manual recommends 128K. Anyone have any ideas about 1. why sync hangs 2. EVA setting for RHEL?

Simon G