Hi Mike,
Since I have moved from LIO to TGT, I can do full ALUA (active/active) of multiple gateways. Of course I have to disable any write back cache at any level (RBD cache and TGT cache). It seem to be safe to disable exclusive lock since each RBD image is accessed only by single client and as long as I know mostly ALUA use RR of I/O path.
Best regards,
On Mar 8, 2018 11:54 PM, "Mike Christie" <mchristi@xxxxxxxxxx> wrote:
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 <mchristi@xxxxxxxxxx>
> *发送时间：*2018-03-07 03:51
> *主题：*Re: iSCSI Multipath (Load Balancing) vs RBD
> Exclusive Lock
> *收件人：*"Lazuardi Nasution"<mrxlazuardin@gmail.com >,"Ceph
> Users"<ceph-users@xxxxxxxxxx.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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