[CentOS] write-back cache question

Thu Feb 17 21:48:09 UTC 2011
James Chase <james at wintercastle.net>

> You can verify your cache policy with MegaCLI tool. Check your output
> from `MegaCli -CfgDsply -a0' command.
>
What a cool tool. It looks like it should be active according to 
MegaCli, though strange that Scott sees his drives in write-back mode 
via CentOS and I do not and I also have these horrific NFS speeds via 
VMWare that so many people have found to be caused by write-back not 
being active...

I don't know what the answer is to this question. I went with iSCSI 
instead of NFS, the benefits being that it trounces my NFS setup 
performance wise, and seems stable despite warnings of high I/O causing 
VMWare to drop the LUN (I tested with bonnie++ as it seems this is an 
effective tool in getting the LUN to drop in VMWare).

Product Name: PERC 5/i Integrated

Memory: 256MB

BBU: Present
...

Default Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU

Current Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU

Access Policy: Read/Write

Disk Cache Policy: Disk's Default