I do get query in my mind why SCSI-3 Reservation does is need to enable in Storage Foundation for Windows (VERITAS Volume Manager)…. We use SCSI-3 PGR in Windows Cluster Servers and you can also see an article which describe about the difference in understanding the concept of SCSI-3 Reservation in Windows Server Cluster 2003 & Failover Cluster Server 2008 – More Info
Let’s talks about the concept of SCSI-3 Persisting Group Reservation from the Veritas Volume Manager prospects.
SCSI-3 PGR works with a concept of Registration and Reservation, host accessing the SCSI-3 Device its registers a key with it and each host registers its own key. Multiple hosts registering keys from a membership, registered hosts can then establish a reservation with SCSI-3 Device Form a membership. Registered hosts can then establish a reservation with the SCSI-3 device. The reservation type is set to “Exclusive Access – Registrants Only“. This means that only some commands to communicate with the device are allowed, and there is only one persistent reservation holder. With SCSI-3 PGR technology, blocking write access can be done by removing a registration from a SCSI-3 device. In the SFW DMP implementation, a host registers the same key for all of its paths to the SCSI-3 device, allowing multiple paths to use it without having to make and release reservations.
This is why we don’t need I/O Fencing SFW HA in Windows…
Let’s See: How we can check the SCSI-3 Reservation on a Sever from Veritas Volume Manager?
When we open the VEA console – we generally in a System Tab
You need to go down and click Control Panel and click Storage Agent
In the right hand side you will see the Control Panel
Click System Settings and go to the SCSI Option and you can view SCSI-2 / SCSI-3 option which is selected.
I was also checking the SCSI-3 PGR from the GUI from the array section but it was not showing up there in VEA.
Then I was wondering why it’s not reflecting in the GUI and then found an article from Symantec More Info which says as below
The setting does not indicate a failure to set the storage array for SCSI-3 PGR and is independent of any requirements to do so.
There are two modes of SCSI in VEA:
DSM “SCSI-2 to SCSI-3” translation mode is used where the application (for example Microsoft Cluster Server 2003) is using SCSI-2 mode, and SFW DSM translates the SCSI-2 to SCSI-3 related reservation in order to allow I/O to use multiple paths on SCSI-3 capable storage. This is set from the registry and is not related to “SCSI-3 mode” setting in VEA. (Refer to the SFW Admin guide for more details.)
VEA “SCSI-3” mode issues SCSI-3 command directly to a DG cluster disk. There is no need to for a DSM to do “SCSI-2 to SCSI-3” translation with this setting. This SCSI-3 mode is not related to DSM “SCSI-2 to SCSI-3” translation mode.
There is a CLI based utility from which you can get the confirmation of the disk reservation status that it has SCSI-3 or not that is SYMCLI
scsicmd -ddisknumber -sscsi_reserved_status
This is very handy tool to work with below are few more commands which will help you out
Perform SCSI-2 bus reset/break reservation
scsicmd -d -sscsi2_clear
Clear SCSI-3 key and SCSI-3 reservation
scsicmd -d -sscsi3_clear
Get standard SCSI Inquiry
scsicmd -d -s12
Please share your review thanks….