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

SCSI-3-1

You need to go down and click Control Panel and click Storage Agent

SCSI-3-2

In the right hand side you will see the Control Panel

SCSI-3-3

 

Click System Settings and go to the SCSI Option and you can view SCSI-2 / SCSI-3 option which is selected.

SCSI-3-4

I was also checking the SCSI-3 PGR from the GUI from the array section but it was not showing up there in VEA.

SCSI- DSMNow in the right had tab we can see the DSM DMP

SCSI- DSM02

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

SCSI- DSM03

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

SCSI- DSM04 - SCSI CMD

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….

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