[stgt] read only access on 1 LUN for multiple initiators

[Tomasz Chmielewski]

On 28.02.2010 20:55, Pasi Kärkkäinen wrote:
> On Sat, Feb 27, 2010 at 12:20:21AM +0200, Kapetanakis Giannis wrote:
>> Hi,
>>
>> This probably have been brought up before, but I couldn't find any info.
>>
>> I'd like to setup multiple initiators (web/ftp cluster) to access
>> read-only the same iscsi target.
>> I would prefer to do this without cluster fs (ie GFS) if possible.
>> However I want to have right access on the target server locally.
>>
>
> This will be difficult. Normal filesystems (ext2, ext3, ext4, xfs, etc)
> are designed to be in use only on one node, so they don't have cluster-aware
> locking, cache flushing etc..
>
> Each server (initiator) will have its own linux kernel cache, so I bet
> your setup won't work very easily.. unless there's some way to completely
> disable all caching in the initiator kernels.
>
> Basicly the problem is the initiators are not aware of the changes made
> to the filesystem, since the changes are made on other systems.

Exactly this is what happens.

You can workaround this by dropping caches on all sides:

echo 3 > /proc/sys/vm/drop_caches

But generally, this is not recommended - use a distributed filesystem 
like GFS, or NFS, or glusterfs instead.


-- 
Tomasz Chmielewski
http://wpkg.org
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