What will happen with VMs if Hyper-V Server R2 loose connection to iSCSI target for few seconds (clustered VMs)?
- Hello,
what will happen with virtual machines if Hyper-V Server R2 loose connection to iSCSI target for few seconds (clustered VMs)? They all will be turned off or maybe is there some failsafe time when iSCSI connection can be renewed? On VMware ESXi (VMs are kept on NFS share) when connection is interrupted and after few seconds online again VMs are still up and I'm wondering how this looks on Hyper-V.
Thanks
Answers
Hi,
Not sure in the scenario which you present below where is the iscsi initiator driver running the guest OS or the parent.
If the initiator is MS iSCSI software initiator – in case of connection loss the initiator waits for 60S (by default, configurable through registries) and within those 60S makes periodic re-connect attempts. If the connection is restored the IO flow continues. If does not at the end of 60S a bus re-enumeration is triggered and if the connection can not be restored the disks are surprise removed.
The wait times are different in case you are using multipathing (MPIO) on top of iSCSI and have multiple sessions to the same target. The bus rescan happens much quicker (15S) in that case so MPIO layer is aware of lost iSCSI sessions (paths in MPIO terminology).
iSCSI Management and Tuning
Vincent Hu
- Marked As Answer byWebio Sunday, November 08, 2009 1:21 PM
All Replies
Hi,
Not sure in the scenario which you present below where is the iscsi initiator driver running the guest OS or the parent.
If the initiator is MS iSCSI software initiator – in case of connection loss the initiator waits for 60S (by default, configurable through registries) and within those 60S makes periodic re-connect attempts. If the connection is restored the IO flow continues. If does not at the end of 60S a bus re-enumeration is triggered and if the connection can not be restored the disks are surprise removed.
The wait times are different in case you are using multipathing (MPIO) on top of iSCSI and have multiple sessions to the same target. The bus rescan happens much quicker (15S) in that case so MPIO layer is aware of lost iSCSI sessions (paths in MPIO terminology).
iSCSI Management and Tuning
Vincent Hu
- Marked As Answer byWebio Sunday, November 08, 2009 1:21 PM
- Thank you. It looks that I was looking for this. I'll test and let you know. I asked about this to have my Windows systems manged by Hyper-V and located on iSCSI target keep alive when I'm rebooting my iSCSI target.
