Re: [PATCH RFC] add support of sheepdog backing store

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



At Thu, 26 Sep 2013 19:29:06 -0700,
ronnie sahlberg wrote:
> 
> On Thu, Sep 26, 2013 at 6:59 PM, Dan Mick <dan.mick@xxxxxxxxxxx> wrote:
> >
> >>> Some might say this had better to be a dynamic loadable
> >>> library. Either is fine by me because it doesn't depend on any
> >>> original C header files.
> >>
> >>
> >> I'm ccing people who would be interested in modular backing
> >> stores, Ronnie Sahlberg and Andy Grover. I think the sheepdog backing
> >> store support doesn't have to be a module because it doesn't create
> >> any new dependencies. Any comments?
> >
> >
> > It seems that you've accomplished this by including structure and constant
> > definitions (and presumably protocol-marshalling routines) in the tgt source
> > file itself, which seems to me to be the wrong way to do it, but it does
> > free you from requiring headers or libraries, so
> > technically speaking, true.
> >
> > I wouldn't write the plugin this way (copying code), but that's me.
> 
> 
> What Dan said!
> Since you don't add any new dependencies it shouldn't matter if this
> is built-in or a module.
> 
> However, you do this at the cost of having a full blown
> re-implementation (or it is a copy?) of a sheepdog client in the
> backing store file.
> I assume there are client libraries for sheepdog available?
> 
> So I think from a maintenance viewpoint, it would probably be better
> if you had the backend just be a thin layer that would call out to and
> link to the sheepdog client library.
> I.e. link to a sheedog library instead of reimplementing it in the backend.
> And in that case then this should be a module.

Thanks for your comment, Dan and Ronnie.

Currently, sheepdog doesn't have its client library. We have a plan to
implement it. But it will take time.

In addition, the backing store support of sheepdog isn't a simple copy
(from QEMU). We can't re-implement it by simple copy because current
sheepdog users, QEMU and tgt, have very different I/O models. e.g.
 QEMU is a heavy user of coroutine.

After implementing the library, the backing store support of sheepdog
can be a module. But for now, this patch would be optimal because it
doesn't increase the cost of tgt maintenance (the patch simply adds a
single file).

Thanks,
Hitoshi
--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux SCSI]     [Linux RAID]     [Linux Clusters]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]

  Powered by Linux