Re: [Nbd] [ANNOUNCE] Ramback: faster than a speeding bullet
- To: "Daniel Phillips" <phillips@...165...>
- Cc: nbd-general@lists.sourceforge.net, Grzegorz Kulewski <kangur@...167...>, linux-kernel@...25..., Chris Friesen <cfriesen@...168...>, Lars Marowsky-Bree <lmb@...122...>, Willy Tarreau <w@...166...>, Alan Cox <alan@...169...>
- Subject: Re: [Nbd] [ANNOUNCE] Ramback: faster than a speeding bullet
- From: "Mike Snitzer" <snitzer@...17...>
- Date: Wed, 12 Mar 2008 10:41:30 -0400
- Message-id: <170fa0d20803120741n1f9f89ban27b18b4b671d48dd@...18...>
- In-reply-to: <200803120117.57644.phillips@...165...>
- References: <200803092346.17556.phillips@...165...> <200803111256.51267.phillips@...165...> <20080311205340.GJ8953@...166...> <200803120117.57644.phillips@...165...>
On 3/12/08, Daniel Phillips <phillips@...165...> wrote:
> On Tuesday 11 March 2008 13:53, Willy Tarreau wrote:
> > BTW, I would say that IMHO nothing here makes RAID impossible to use :-)
> > Just wire 2 of these beasts to a central server with 10 Gbps NICs and
> > you have a nice server :-)
>
>
> Right. See ddraid. It is in the pipeline, but everything takes time.
> We also need to reroll NBD complete with deadlock fixes before I feel
> good about that.
You've eluded to NBD needing deadlock fixes quite a few times in the
past. I've even had some discussions with you on where you see NBD
lacking (userspace nbd-server doesn't lock memory or set PF_MEMALLOC,
etc). But I've lost track of what changes you have in mind for NBD.
Are you talking about a complete re-write or do you have specific
patches that will salvage the existing NBD client and/or server? Has
this work already been done and you just need to dust it off?
As an aside, using a kernel with the new per bdi dirty page accounting
I've not been able to hit any deadlock scenarios with NBD. Am I not
trying hard enough? Or are they now mythical? If real, do you have a
reproducible scenario that will cause NBD to deadlock?
I'm not interested in swap over NBD (e.g. network memory reserves?)
because in practice I've found that the VM doesn't allow non-swap NBD
use-cases to actually need that "netvm" sophistication... any other
workload that deadlocks NBD would interesting.
thanks,
Mike
Reply to: