Possible use for memcache?

David Phillips david at acz.org
Sun Nov 27 22:42:51 PST 2005

On 11/27/05, mike <mike503 at gmail.com> wrote:
> Isn't that basically what file locking mechanisms are? Cached
> placeholders claiming a file is in use ("cached"  used loosely, as it
> can be any amount of time I suppose)
> This would be a distributed mechanism for claiming ownership of files
> and only allowing that one path to the file; if the cache expires, the
> server dies, etc, another one will pick up in it's place. I don't see
> a problem with that, even a cache of 60 seconds would alleviate two
> separate servers trying to access the same file.

If I understand your approach correctly, it seems to lack consistency.
 What happens when two servers try to access the same file due to
memcached dying?  How do you handle the switch over?

It sounds like you have some requirements and non-requirements in mind
already.  Once you formally identify all of those, it becomes much
easier to create a matching solution.  There might be a simpler method
given your constraints.

> I'd pair Lustre with GFS and OCFS. The problem is, GFS is Linux-only.
> Same with Lustre (although a BSD port is supposedly in the works) -
> OCFS is just barely public now it seems (in the -mm kernels and in
> Ubuntu)

You would actually want OCFS2, as OCFS is specifically designed for Oracle.

> Again - what I want is pretty simple (on a high level) - something as
> simple as NFS, but the ability to have N number of servers access the
> same hardware.

What exactly do you mean by "the same hardware"?

> Actually, I don't need a lot of local storage added. I'm still
> planning on a centralized storage mechanism (with redundancy built in
> the hardware layer) - but Lustre I believe would solve what you said
> as well (it appears to be able to support adding capacity from any
> disks on the network as long as it runs the software)

If you're going with centralized storage, what's wrong with using a
single NFS server to access it?  A NetApp or EMC product seems
appropriate here.

This is an interesting discussion and topic, but I still don't have a
clear understanding of the problem you are trying to solve.

> AoE is what I would hope to use, but may have to use iSCSI since it's
> better supported. There's a thread I found whilst researching this
> stuff where someone vehemently was trying to disspell supposed truths
> about AoE and it's multi-targetting and other features.

Can you provide a link?

David Phillips <david at acz.org>

More information about the memcached mailing list