[ceph-users] Using FC with LIO targets

Frédéric Nass frederic.nass at univ-lorraine.fr
Wed Oct 31 06:28:12 PDT 2018


Hi Mike,

Thank you for your answer. I thought maybe FC would just be the transport protocol to LIO and all would be fine but I forgot the tcmu-runner part which I suppose is where some iSCSI specifics were hard coded.

FC was interesting in the way that (when already set) it would avoid having to dedicate specific NICs to iSCSI traffic. Nowadays, many ESXi blades only have 2x 10Gbs or 25Gbs NICs configured as LACP LAG in ESXi.
So dedicating NICs to iSCSI traffic may not be easy anymore. I don’t know. We’ll see how DELL NPAR can help us creating virtual hardware NICs that we can use for ISCSI traffic.

Best regards,
Frédéric.

> Le 31 oct. 2018 à 04:59, Mike Christie <mchristi at redhat.com> a écrit :
> 
> On 10/28/2018 03:18 AM, Frédéric Nass wrote:
>> Hello Mike, Jason,
>> 
>> Assuming we adapt the current LIO configuration scripts and put QLogic HBAs in our SCSI targets, could we use FC instead of iSCSI as a SCSI transport protocol with LIO ? Would this still work with multipathing and ALUA ?
>> Do you see any issues coming from this type of configuration ?
> 
> The FC drivers have a similar problem as iscsi.
> 
> The general problem is making sure the transport paths are flushed when
> we failover/back. I had thought using explicit failover would fix this,
> but for vpshere HA type of setups and for the single host with multiple
> initiator ports to connected to the same target port we still hit issues.
> 
> For iscsi, I am working on this patchset (maybe half is now merged but
> the patchset is larger due to some other requested fixes in sort of
> related code):
> 
> https://www.spinics.net/lists/target-devel/msg16943.html
> 
> where from userspace we can flush the iscsi paths when performing
> failover so we know there are no stale IOs in that iscsi/code path.
> 
> For FC drivers I was planning something similar where we would send a FC
> echo like we do for the iscsi nop.
> 
> If you are asking if you can just drop in one of the FC target drivers
> into the ceph-iscsi-config/cli/tcmu-runner stuff then it would not work,
> because there are a lot of places where iscsi references are hard coded now.
> 
> 
> 
>> Best regards,
>> Frédéric.
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>> 
> 



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