official way to load aoe module?

[Amos Shapira]

On 22 August 2010 23:22, Oleg Goldshmidt <pub at goldshmidt.org> wrote:
>
> On Sun, Aug 22, 2010 at 2:25 PM, Amos Shapira <amos.shapira at gmail.com> wrote:
>
> > We are a little concerned about the situation of two guests mounting
> > the ext3 and starting to manipulate the sqlite files on it in
> > parallel.
>
> I think you should be *very* concerned about the situation where 2
> guests mount an ext3 partition and start to manipulate files
> *sequentially*. It looks like you *are* concerned (rightly), since you
> wrote that only one client *mounts* the partition at a time.

Yes. But apart from hoping that RHCS does its job right, there is
nothing preventing other guests from mounting the same partition in
parallel.

>
> > Another option was to allow all guests to mount the file
> > system read/write but carefully configure each guest to "own"
> > different files or directories of sqlite files on the FS.
>
> What if one starts, e.g., creating files or appending content to
> existing files (and allocating new blocks, etc., in the process)? The
> other clients won't be aware of it.

That's why we looked at cluster-aware file systems in form of GFS but
decided the performance hit is too great to go with it. A brief look
at OCFS installation steps gave an impression that it isn't trivial or
well supported on CentOS 5.

>
> I admit I have not thought long and hard about it, but it sounds
> dangerous to me.

It is. As was pointed out earlier in this thread - a large part of the
"file system" is about how the file system module "caches" information
in memory and synchronises it on the disk. If it's not a cluster-aware
file system then parallel mounting is equivalent to opening the LV or
device by an application and randomly starting to write data on it.

Cheers,

--Amos