On Thu, Nov 2, 2017 at 1:21 AM koukou73gr <koukou7...@yahoo.com> wrote:
> The scenario is actually a bit different, see: > > Let's assume size=2, min_size=1 > -We are looking at pg "A" acting [1, 2] > -osd 1 goes down > -osd 2 accepts a write for pg "A" > -osd 2 goes down > -osd 1 comes back up, while osd 2 still down > -osd 1 has no way to know osd 2 accepted a write in pg "A" > -osd 1 accepts a new write to pg "A" > -osd 2 comes back up. > > bang! osd 1 and 2 now have different views of pg "A" but both claim to > have current data. In this case, OSD 1 will not accept IO precisely because it can not prove it has the current data. That is the basic purpose of OSD peering and holds in all cases. -Greg > > -K. > > On 2017-11-01 20:27, Denes Dolhay wrote: > > Hello, > > > > I have a trick question for Mr. Turner's scenario: > > Let's assume size=2, min_size=1 > > -We are looking at pg "A" acting [1, 2] > > -osd 1 goes down, OK > > -osd 1 comes back up, backfill of pg "A" commences from osd 2 to osd 1, > OK > > -osd 2 goes down (and therefore pg "A" 's backfill to osd 1 is > > incomplete and stopped) not OK, but this is the case... > > --> In this event, why does osd 1 accept IO to pg "A" knowing full well, > > that it's data is outdated and will cause an inconsistent state? > > Wouldn't it be prudent to deny io to pg "A" until either > > -osd 2 comes back (therefore we have a clean osd in the acting group) > > ... backfill would continue to osd 1 of course > > -or data in pg "A" is manually marked as lost, and then continues > > operation from osd 1 's (outdated) copy? > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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