Smart Array P400 cache ratios and hysical Drive Write Caching

[Ed Roche]

Hi guys

We are experiencing high 'average disk Q lengths' on one server and HP has suggested changing the cache ratio from '100% Read, 0% Write' to 50/50 on our P400.

The option is not in the Array Config Util, just says 100 % Read, 0 % Write. Am I missing something? HP says theres a battery onboard, Systems Management says no battery present. 256MB RAM. See attached screen shot.

Also, for a regular file server, is there a point in enabling Physical Drive Write Caching? Im having a problem where the server hangs from time to time for 7-10 seconds. Upon closer inspection I see that the 'average disk Q lengths' is maxed for short bursts at the time we experience this.

Thanks

[KarloChacon]

hi

no you cannot change it because your controller doesn't have battery... you would be able to change read/write if your controller had battery which does not

so you need either

Battery-backed write cache upgrade
383280-B21

or

512MB Battery-backed write cache upgrade
405148-B21

regards

[Ed Roche]

No battery installed