On Mon, 28 May 2018 23:02:36 -0400 Mike Snitzer <snit...@redhat.com> wrote:
> On Mon, May 28 2018 at 9:19pm -0400, > Martin K. Petersen <martin.peter...@oracle.com> wrote: > > > > > Mike, > > > > I understand and appreciate your position but I still don't think > > the arguments for enabling DM multipath are sufficiently > > compelling. The whole point of ANA is for things to be plug and > > play without any admin intervention whatsoever. > > > > I also think we're getting ahead of ourselves a bit. The assumption > > seems to be that NVMe ANA devices are going to be broken--or that > > they will require the same amount of tweaking as SCSI devices--and > > therefore DM multipath support is inevitable. However, I'm not sure > > that will be the case. > > > > > Thing is you really don't get to dictate that to the industry. > > > Sorry. > > > > We are in the fortunate position of being able to influence how the > > spec is written. It's a great opportunity to fix the mistakes of > > the past in SCSI. And to encourage the industry to ship products > > that don't need the current level of manual configuration and > > complex management. > > > > So I am in favor of Johannes' patches *if* we get to the point > > where a Plan B is needed. But I am not entirely convinced that's > > the case just yet. Let's see some more ANA devices first. And once > > we do, we are also in a position where we can put some pressure on > > the vendors to either amend the specification or fix their > > implementations to work with ANA. > > ANA really isn't a motivating factor for whether or not to apply this > patch. So no, I don't have any interest in waiting to apply it. > Correct. That patch is _not_ to work around any perceived incompability on the OS side. The patch is primarily to give _admins_ a choice. Some installations like hosting providers etc are running quite complex scenarios, most of which are highly automated. So for those there is a real benefit to be able to use dm-multipathing for NVMe; they are totally fine with having a performance impact if they can avoid to rewrite their infrastructure. Cheers, Hannes
