[JDSS][DSS V7] Hyper-V tuning

Additional information:

• product name: JovianDSS / DSS V7
• product version: all
• build: all

Subject:

Hyper-V tuning recommendations for JovianDSS & DSS V7.

Contents:

1. ISCSI proper values script for Hyper-V.

NOTE:
Please proceed with the actions during a maintenance window as there might be a connection loss present.

You can find the script in the attachment, it is optimized for default ISCSI session settings, parameters below:

MaxRequestHoldTime = 240; <= not present in JovianDSS / DSS V7
SrbTimeoutDelta = 120; <= not present in JovianDSS / DSS V7
LinkDownTime = 240; <= not present in JovianDSS / DSS V7
WMIRequestTimeout = 15; <= not present in JovianDSS / DSS V7
MaxTransferLength = 262144;
MaxBurstLength = 1048576;
FirstBurstLength = 65536;
MaxRecvDataSegmentLength = 262144

Please check if the parameters on the ISCSI session in JovianDSS / DSS V7 and then run the script on the initiator side [Hyper-V], so the value matches: 
[ JovianDSS CLI console: CTRL+ALT+W > Tuning options > iSCSI target options > Target options ]
[ DSS V7 CLI Console > CTRL+ALT+W > Tuning options > iSCSI daemon options > Target options ]

Then, reboot the initiator’s host [Hyper-V] in order to apply the proper configuration. 
 

2. Keep in mind to set the same block size in JovianDSS / DSS V7, Hyper-V datastore, and actual VMs [their filesystem]. This has a large impact on overall performance

3. Make sure to only use STATIC paths for iSCSI sessions. Never use DYNAMIC ones, as this may cause problems with failover and data access

4. ​​When using Hyper-V Cluster with JovianDSS please enable the PRS option in JovianDSS GUI.
   
   [ JovianDSS WebGUI > Failover Settings > SCSI-3 Persistent Reservation Synchronization > toggle "Enable Persistent Reservation Synchronization"]

5. When using Hyper-V Cluster with DSS V7 please make sure to enable PRS option in DSS V7 CLI.
   
   [ DSS V7 CLI Console > CTRL+ALT+X > 17. PRS management > select "Enabled" > press "Save changes" ]

6. When using Windows Exchange Server we recommend increasing Windows disk TimeOutValue to 180 seconds. 
   
   Detailed guide: Windows Disk Timeouts and Exchange Server