topic Re: Turning off writeback cache on HSG80 in Operating System - OpenVMS

Turning off writeback cache on HSG80

Glenn Tice — Fri, 11 Feb 2005 12:07:55 GMT

We have a HSG80 (V86F-1) based array with a single controller and cache. I'm concerned that a controller/cache/ECB failure will result in data loss. If I turn off writeback caching (set d0 nowriteback_cache), will this ensure data integrity if the cache fails?
I presume that the host will only be informed that the write is sucessful when it is physically written.

Re: Turning off writeback cache on HSG80

Garry Fruth — Fri, 11 Feb 2005 12:46:24 GMT

I agree with your interpretation.

Re: Turning off writeback cache on HSG80

Andreas Fassl — Sat, 12 Feb 2005 16:15:08 GMT

Hi Glenn,

this is the reason you'll always should configure a system with a battery backup.
The battery has to be replaced on a regular base. If the battery is fine, you'll see no loss of data.

If you turn of write_back cache, you'll experience a major loss of write performance.

Best regards

Andreas

Re: Turning off writeback cache on HSG80

Uwe Zessin — Sun, 13 Feb 2005 05:43:14 GMT

A battery backup won't help if the controller or especially the cache module fails. NOWRITEBACK_CACHE will decrease the likelyhood of data corruption due to write holes.