Re: Disable read/write caching to disk?

Bjoern Koenig wrote:
> Eric Anderson wrote:
> 
>> Bjoern Koenig wrote:
>>
>> Thanks.. I've just read (quickly) both man pages.  It seems as though 
>> you are suggesting disabling the physical disk caching, which should 
>> not make a difference in my case.  The disk would report whatever it 
>> needs to report to either host, and those should be in sync.
> 
> 
> Oh, I'm sorry. I have misunderstood you then.
> 
>> When I mount the filesystem on host B ro, it shows me the filesystem 
>> as of the time that I mounted it ro.  Any subsequent changes on host A 
>> (which has it mounted rw) are not seem on host B unless I unmount and 
>> mount again on host B.  This seems like a FreeBSD feature and not a 
>> general scsi feature.
> 
> 
> By what mechanism do you mount the partitions remote? I'm not very 
> experienced with this. I'm thinking of a typical network file system or 
> GEOM gate.

I have two servers connected directly to a fiber channel disk array 
(containing 16 WD Raptor SATA drives in RAID0+1 configuration).  Each 
server sees the same exact luns, so I create the partition and 
filesystem from host A.  I mount it (rw) on host A.  Then, if I do a:
camcontrol rescan all
on host B, I pick up the fiber channel disk and it sees it as da0 (just 
like on host A).  I can then mount it rw or ro on host B.

I think using GEOM gate might give a similar situation.

Eric


-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
A lost ounce of gold may be found, a lost moment of time never.
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