On 06/10/2015 05:02 PM, Ewan Milne wrote: > On Mon, 2015-04-20 at 07:58 +0200, Hannes Reinecke wrote: >> On 04/19/2015 12:56 AM, Christophe Varoqui wrote: >>> About five years ago, we faced a somewhat simular issue with >>> Symmetrix arrays, where the replicated LU of a SRDF pair (R2) was >>> flagged read-only by the kernel upon discovery. Splitting the pair >>> with a symcli command made the LU read-write from the array >>> controller point of view, but the Linux kernel would not promote it >>> read-write dynamically. >>> >>> I don't know if the Symmetrix array also use a unit attention to >>> signal the change to the initiators. If it does, it might be worth >>> trying to address both the 3par peer persistance and the Symmetrix >>> SRDF situations. >>> >>> On the other hand, if the SRDF R2 rw promotion issue has been fixed >>> since, the patch might give guidance about where/how to plug the >>> 3par peer persistance ghost path rescans. >>> >> It's not only that; if you are faced with LUNs in standby even the >> kernel wouldn't detect them properly. >> >> I'm currently debugging this issue and will have an update soon(-ish). > > I have a patch set to have the kernel automatically rescan the device > when the ALUA state changes to an ACTIVE state, if it couldn't read > capacity when the device was initially probed. I've had it for a while, > but I haven't had *any* response from the vendor if it actually works > with their product, so I haven't posted it to the list for review yet. > Please hold off that patchset. I've posted the ALUA update patchset a while ago, and are working on including the suggestions from hch. Please check if that patchset fixes the issue. Additionally, I've got some patches for lio-target which will blank out the READ CAPACITY command when in standby; with that one has an easy testbed for this kind of issues. > I did point out to them that the T10 spec does not *prohibit* supporting > the READ CAPACITY command in the ALUA standby state, which would avoid > the problem, and is what other vendors seem to do. However, they then > raised the issue that if the capacity changes in the standby state then > they should be generating the capacity changed UA, etc and you can sort > of see their point of why this gets complicated. > Which is actually not true. The capacity did _not_ change, it's just the command which isn't supported. If the command was supported and would have reported a size of '0' in standby _then_ it would have been a capacity change. But that's not the case here. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
