How do I create a VCMDB device during installation?

Question

What I understand is that we would create one 3MB device and change the attribute to VCMDB(set attribute dev device_no attr =VCMDB)to make that VCMDB device and then would run vcmdb init command to create the VCMDB database.However,I found the note in one EMC document taht the VCMDB would reside in SFS volume.Here my confusion is how we would create one device in SFS volume where the VCMDB database would reside.

Thanks

Swarup

dynamox · Answer

why do you need to create a vcmdb device ?

RobertDudley · Answer

The SFS volumes are not mapped to a host so the 3 MB device is used as a command pass-thru device to get the data into the SFS volumes.  Normally at install a VCM volume is defined and you would then run the init command against it.  You can only have one VCM device in a storage array so check for one prior to trying to set that flag against a device.  If you have issues finding it I would suggest you either open a case or engage your local account team.

19761 · Answer

Thanks Robert for your reply.Actually I just want to know the procedure of creating VCM volume at installation time.In my environmemt,VCM is already set up and no need to create any more VCM.Just want to know the process-The creation of vcm  happens thru  bin file changes or SYMCLI.

Rasmmacias · Answer

Hello, You can see the EMC solution:emc204637: Symmetrix Configuration recommendations when mapping the VCM or ACLX database gatekeeper volume (VCM or ACLX gatekeeper) to host channels:

"Symmetrix Configuration recommendations when mapping the VCM or ACLX database gatekeeper volume (VCM or ACLX gatekeeper) to host channels."

ID:	emc204637
Domain:	GS Primus Database
Usage Count:	22
Class:	3.X Compatibility
Conflicts:	0

Status:	Approved
Audience:	Customer
Owner:	CORP\leem1 (Lee, Michael - E 4/6/01)
Product:	Solutions Enabler SYMCLI, Symmetrix, Symmetrix Config
Author:	CORP\leem1 (Lee, Michael - E 4/6/01)
Date Created:	1/6/2009
Modified By:	CORP\leem1 (Lee, Michael - E 4/6/01)
Date Modified:	9/15/2010
Shared:	Yes
RCA Status:	Not Started
RCA Cause:	None
Review Frequency:	Medium
ETA:	None
Bug Tracking Number:	None
NGOE Product/Version:	None

Goal

Symmetrix Configuration recommendations when mapping the VCM or ACLX database gatekeeper volume (VCM or ACLX gatekeeper) to host channels.

What is best practice when mapping the VCMDB or ACLX volume (VCM or ACLX gatekeeper) to host channels?

SLS Support

Symmetrix Configuration recommendations when assigning the VCMDB or ACLX to fibre/iSCSI paths.

Should the VCMDB or ACLX be write disabled?

Does the VCMDB or ACLX need to be assigned to all fibre/ iSCSI paths?

Why does the VCMDB or ACLX need to be assigned to host channels in a PowerPath environment?

Are there are issues associated with leaving the VCMDB or ACLX volume assigned to all fibre/iSCSI paths?

Fact

EMC SW: Solutions Enabler

Product: Symmetrix DMX Series

Product: Symmetrix DMX-3

Product: Symmetrix DMX-4

Product: Symmetrix VMAX Series

Symptom

Potential host application or system crash.

SLS Support

Change

Online change host addressing.

Online Symmetrix Disk Reallocation (SDR) reassign.

Cause

The following two statements are from the latest EMC Solutions Enabler Symmetrix Array Controls CLI Product Guide available on Powerlink (go to Home > Support > Technical Documentation and Advisories > Software ~ S ~ Documentation > Solutions Enabler > General Reference):

Fix

The Symmetrix configuration recommendation for EMC Global Service staff is to assign only the VCMDB (Volume Control Manager Data Base) or ACLX (Access Control Logix) gatekeeper volume to the Administration Host or Control Station. The assigned VCMDB or ACLX will be visible to the Administration Host and allow the initial setup of the device masking environment. Remember that once the VCM or ACLX Edit Director flag (Enable FibrePath on this Port) is enabled on a fibre channel (FA) or iSCSI (SE) port the only visible device will be the assigned VCMDB or ACLX gatekeeper volume.

With Solutions Enabler Version 5.3 and above and Enginuity 5670 and above, the VCM Database Volume (VCMDB or VCM gatekeeper) or ACLX device does NOT need to be assigned to all fibre or iSCSI paths. At these software levels, communication between the host and VCM database is via syscalls using any available FBA gatekeeper device.

The recommendation in the Solutions Enabler manual to map the VCMDB to all paths in a PowerPath environment is due to the behavior of the symmask discover hba command (used to determine the HBA WWNs). In a PowerPath environment (without the VCMDB assigned) this command may be issued down one host path and returned on a different host path, thereby returning the incorrect WWN information. If the VCMDB is assigned to the fibre or iSCSI channel, this I/O re-direction by PowerPath will NOT occur during this command.
Note that the symmask hba commands are not required for a device masking operation. If the VCMDB is unassigned in a PowerPath environment, then alternate methods of determining the attached WWNs can be used instead. Note that the VCM gatekeeper can also be unassigned from any path once device masking has been initially configured.
Since the release of Enginuity 5771 and DMX-3, the physical VCM gatekeeper volume no longer contains the actual device masking database. This information is stored on the internal Symmetrix File System (SFS) volumes and the content is only accessible via syscalls (using any available gatekeeper device). Since Enginuity 5771, the VCM gatekeeper is no longer automatically write disabled when mapped to a host channel. This is by EMC Engineering design.
This behavior has been seen to vary at Enginuity 5772 and 5773 with the VCM gatekeeper sometimes observed as write disabled (for example, after the VCMDB volume is first created in the bin file or when the VCM database content is first initialized from the host). However, this is NOT consistent and the VCMDB may become write enabled again, say after an online configuration change.
EMC Engineering has stated that the VCM gatekeeper is no longer automatically write disabled by the Enginuity code because the database content is securely stored in the SFS volumes and only accessible via syscalls. The database content CANNOT be affected by normal host commands or I/O. Therefore, labeling the VCM gatekeeper from a host or creating a file system on this write enabled volume does NOT affect device masking operations.
However, if the VCM gatekeeper is assigned to multiple fibre or iSCSI paths, you are therefore potentially sharing a write enabled volume between different hosts and different host types. This has caused data corruption and crashed hosts. (The impact depends on the host data/host label written to the VCMDB volume and the different host types involved.) If the VCM gatekeeper is assigned to multiple host paths, one avoidance is to manually set the assigned VCM gatekeeper volume write disabled on the fibre or iSCSI paths via Solutions Enabler commands or via EMC Inlines commands. This avoidance does NOT affect device masking operations. However, this is not a permanent fix, as the volume may become write enabled on these paths again. Therefore, the Best Practice recommendation is never sharing the VCM gatekeeper between multiple hosts and assigning only the VCM gatekeeper volume to the Administration Host.

Note

Field Support:

For full details on all of the above issues and their resolutions, contact your local Config RTS or Configuration Field Support Specialist (FSS).

SLS Support

mlee2 · Answer

Hi Swarup,I just stumbled across this older discussion, and you will have (hopefully) already determined the answer, but I thought I should clarify the situation (especially since I wrote the solution appended here ).For DMX-3 and later models the VCMDB or ACLX gatekeeper volume is 3 or 6 cylinders. The same size as your normal Solutions Enabler gatekeepers. You are correct the onlydistinction between this volume and any normal gatekeeper is the addition of the VCMDB or ACLX device attribute.As noted in the solution (or as buried in the solution ) the actual Volume Control Manager / Access Control Logix database resides on the EMC internal SFS volumes. Access to the databases is via syscalls and these syscalls can be issued through any host accessible gatekeeper volume (it does not have to be via the VCMDB or ACLX gatekeeper). The solution therefore goes into more detail as to why we need the one-per-SymmetrixVCMDB or ACLX gatekeeper volume and whether it should be assigned to just some or all channels.Suffice it to say that the EMC CE/IDE/FSS who performs your original Symmetrix installation should have created and assigned the VCMDB or ACLX gatekeeper volume on one or more channels for you. It would be very rare for an EMC CE/IDE/FSS to notcreate (and assign) the VCMDB or ACLX gatekeeper device.A minimum installation (new install bin file) would include the EMC internal PWRVLT and SFS volumes, the VCMDB or ACLX gatekeeper volume, and standard FBA gatekeepers. This would allow you to discover the Symmetrix and start provisioning your own storage.Again, you are 100% correct and Solutions Enabler allows you to convert a device into a VCMDB or ACLX device, however this should be unnecessary.Now, I am not suggesting that your local EMC CE/IDE/FSS did not install the Symmetrix correctly, but (as Robert suggested) your local support representative should be your first port of call if you don't have the correct access or cannot see the device / device types you expected to see.Best Regards,Michael.

Symmetrix

How do I create a VCMDB device during installation?

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