Hi Mike, So for now only suse kernel with target_rbd_core and tcmu-runner can run active/passive multipath safely? I am a newbie to iscsi. I think the stuck io get excuted cause overwrite problem can happen with both active/active and active/passive. What makes the active/passive safer than active/active? What mechanism should be implement to avoid the problem with active/passive and active/active multipath? 2018-03-10
shadowlin 发件人：Mike Christie <mchri...@redhat.com> 发送时间：2018-03-09 00:54 主题：Re: [ceph-users] iSCSI Multipath (Load Balancing) vs RBD Exclusive Lock 收件人："shadow_lin"<shadow_...@163.com>,"Lazuardi Nasution"<mrxlazuar...@gmail.com>,"Ceph Users"<ceph-users@lists.ceph.com> 抄送： On 03/07/2018 09:24 AM, shadow_lin wrote: > Hi Christie, > Is it safe to use active/passive multipath with krbd with exclusive lock > for lio/tgt/scst/tcmu? No. We tried to use lio and krbd initially, but there is a issue where IO might get stuck in the target/block layer and get executed after new IO. So for lio, tgt and tcmu it is not safe as is right now. We could add some code tcmu's file_example handler which can be used with krbd so it works like the rbd one. I do know enough about SCST right now. > Is it safe to use active/active multipath If use suse kernel with > target_core_rbd? > Thanks. > > 2018-03-07 > ------------------------------------------------------------------------ > shadowlin > > ------------------------------------------------------------------------ > > *发件人：*Mike Christie <mchri...@redhat.com> > *发送时间：*2018-03-07 03:51 > *主题：*Re: [ceph-users] iSCSI Multipath (Load Balancing) vs RBD > Exclusive Lock > *收件人：*"Lazuardi Nasution"<mrxlazuar...@gmail.com>,"Ceph > Users"<ceph-users@lists.ceph.com> > *抄送：* > > On 03/06/2018 01:17 PM, Lazuardi Nasution wrote: > > Hi, > > > > I want to do load balanced multipathing (multiple iSCSI > gateway/exporter > > nodes) of iSCSI backed with RBD images. Should I disable exclusive lock > > > feature? What if I don't disable that feature? I'm using TGT (manual > > way) since I get so many CPU stuck error messages when I was using LIO. > > > > > You are using LIO/TGT with krbd right? > > You cannot or shouldn't do active/active multipathing. If you have the > lock enabled then it bounces between paths for each IO and will be slow. > If you do not have it enabled then you can end up with stale IO > overwriting current data. > > > >
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