Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
- To: Christoph Hellwig <hch@...1270...>
- Cc: "nbd-general@lists.sourceforge.net" <nbd-general@lists.sourceforge.net>, Josef Bacik <jbacik@...2204...>, "linux-kernel@...25..." <linux-kernel@...25...>, linux-block@...25..., mpa@...1897..., Wouter Verhelst <w@...112...>, kernel-team@...2204...
- Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
- From: Alex Bligh <alex@...872...>
- Date: Thu, 15 Sep 2016 13:44:29 +0100
- Message-id: <DA0880DA-700F-4989-9326-68F5F7A55F25@...872...>
- In-reply-to: <20160915124103.GA20657@...1270...>
- References: <20160909200203.phhvodsfs7ymukfp@...3...> <20160915104935.ohuwgq2chsedz6fl@...3...> <20160915113807.GA23259@...1270...> <20160915115514.7hba23nqvvwfhb5z@...3...> <20160915120125.GA31044@...1270...> <20160915122120.4h3ykbewaavjk5nx@...3...> <20160915122304.GA15501@...1270...> <2ABB8966-5C20-45A7-BB4C-6882F042905D@...872...> <20160915123646.GA10394@...1270...> <C48DD624-6EDF-4EED-B474-8BEA021F00F0@...872...> <20160915124103.GA20657@...1270...>
> On 15 Sep 2016, at 13:41, Christoph Hellwig <hch@...1270...> wrote:
>
> On Thu, Sep 15, 2016 at 01:39:11PM +0100, Alex Bligh wrote:
>> That's probably right in the case of file-based back ends that
>> are running on a Linux OS. But gonbdserver for instance supports
>> (e.g.) Ceph based backends, where each connection might be talking
>> to a completely separate ceph node, and there may be no cache
>> consistency between connections.
>
> Yes, if you don't have a cache coherent backend you are generally
> screwed with a multiqueue protocol.
I wonder if the ability to support multiqueue should be visible
in the negotiation stage. That would allow the client to refuse
to select multiqueue where it isn't safe.
Wouter?
--
Alex Bligh
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