Re: [Aoetools-discuss] problem with kvblade

[Ed C. <ec...@co...>]

On Thu, Feb 12, 2009 at 12:33:22PM +0000, maht lawless wrote:
> er krishna wrote:
> 
> > Can Anyone Please tell me the answer of following qustions :
> >
> >
> > 1) When we access AOE target device then while acessing it, is it 
> > necessary to first unmount it from the server pc , and then use on 
> > client nodes ? Why ? Does this prevent file system corruption or we 
> > can do it without unmounting it.
> 
> 
> Imagine your HD being connected to two IDE cables from 2 machines at 
> once, then you'll understand

Yes, and Krishna, the filesystem corruption comes from the fact that
almost all filesystems are used by "caching" the filesystem
information in RAM.  If the cached information in two different hosts
doesn't match, they had better not commit the conflicting information
to persistent storage.

If you're asking whether it's better to do RAID over multiple,
independent block devices on the AoE target or on the AoE initiator,
it depends on what you're doing.  Often it's more efficient to do RAID
as close as possible to the hard drives, meaning you'd do it on the
AoE target.  (There is a related optimization issue of getting writes
to be read-free that you can read about in the archives for this
mailing list.)

-- 
  Ed Cashin <ec...@co...>