EMC Symmetrix: VCMDB and ACLX

VCMDB:  Volume Control Manager Database

ACLX:  Access Control Logix

VCM:  Volume Control Manager device (where the database resides)

VCM Gatekeeper:  Volume Control Manager Gatekeeper (database doesn’t reside on these devices)

SFS Volumes:  Symmetrix File System Volumes

If you work with EMC Symmetrix systems, you know the importance of VCMDB. Introduced with Symmetrix 4.0 and used in every generation after that, VCMDB stands for Volume Control Manager Database). Also in the latest generation of systems the VCM device is at times also referenced as VCM Gatekeeper.

VCMDB is a relatively small device that is created on the Symmetrix system that allows for hosts access to various devices on the Symmetrix. VCMDB keeps an inventory of which devices have access to which host (HBA’s). Without a VCMDB in place, host systems will not be able to access the Symmetrix. The VCMDB should be backed up on regular intervals and would be helpful in a rainy day.

The VCMDB device size grew along with new generations of Symmetrix systems that got introduced, primarily a means to keep a track of more supported devices (hypers / splits) on these platforms. With the introduction of Symmetrix V-Max, the VCMDB concept is now a bit changed to ACLX (Access Control Logix). Access Logix is being used on the Clariion systems for years now.

Here are a few things to consider with VCMDB

  • On the older Symmetrix systems (4.0, 4.8, 5.0 and 5.5), the VCMDB (device) is mapped to all the channels, host
  • In these systems the VCMDB access is typically restricted by Volume Logix or ACL (access control lists)
  • With the Symmetrix DMX, DMX2 Systems — Enginuity Code 5670, 5671 the VCM device only requires to be mapped to the Management stations
  • Management stations include SYMCLI Server / Ionix Control Center Server / Symmetrix Management Console
  • At all given times on the DMX, DMX2 platforms, the VCMDB would need to be mapped to at least one station to perform online SDDR changes. Alternatively this problem of not having device mapped to at least one host can also be fixed by the PSE lab
  • Mapping VCMDB to multiple hosts, channels may make the device venerable to crashes, potential tampering, device attributes and data change
  • You can write disable VCMDB to avoid the potential of the above
  • With these systems, the host can communicate to the VCMDB via Syscalls
  • The VCM Edit Director Flag (fibrepath) needs to be enabled for management stations to see VCM device
  • The database (device masking database) of the VCMDB resides on the  SFS volumes. This feature was introduced with DMX-3 / DMX-4 (5772 version of microcode). A 6 cylinder VCM Gatekeeper device is okay to use with these versions of microcode.
  • Starting Symmetrix V-Max systems, the concept of ACLX was introducted for Auto Provisioning etc.
  • VCM volumes are required to be mirrored devices like SFS volumes

Various different types of VCMDB

Type 0, Type 1, Type 2, Type 3, Type 4, Type 5, Type 6

  • Type 0:  Symmetrix 4.0, 32 Director System, 16 cylinder device size, Volume Logix 2.x
  • Type 1:  Symmetrix 4.8, 64 Director System, 16 cylinder device size, ESN Manager 1.x
  • Type 2:  Symmetrix 5.0/5.5, 64 Director System, 16 cylinder device size, ESN Manager 2.x
  • Type 3:  Symmetrix DMX, supports 32 fibre/ 32 iSCSI initiator records per port, 24 cylinder device in size. Enginuity 5569, Solutions Enabler 5.2, Support 8000 devices
  • Type 4:  Symmetrix DMX/DMX-2, supports 64 fibre/ 128 iSCSI initiator records per port, 48 cylinder device in size. Enginuity 5670, Solutions Enabler 5.3, Supports 8000 devices
  • Type 5:  Symmetrix DMX/DMX-2, supports 64 fibre / 128 iSCSI initiator records per port, 96 cylinder device in size, Enginuity 5671, Solutions Enabler 6.0, Supports 16000 devices
  • Type 6:  Symmetrix DMX-3, DMX-4, supports 256 fibre / 512 iSCSI initiator records per port, 96 cylinder device in size, Enginuity 5771, 5772 Solutions Enabler 6.0, Supports 64000 devices

Notes about various Types of VCMDB

  • Type 3 of VCMDB can be converted to Type 4 VCMDB (code upgrade from 5669 to 5670 to 5671)
  • Solutions enabler 5.2 and Solutions Enabler 5.3 can read/write Type 3 VCMDB
  • Solutions enabler 5.3 can read/write Type 4 VCMDB
  • VCMDB device is recommended to be a certain size, but it is okay to use a larger size device if no choices are available.

Converting various types of VCMDB using SymCLI

  • If the device cylinder size is equal with a conversion you are attempting, the following will help you convert your VCMDB from type x to type y.
    • Backup the device
    • symmaskdb —sid <symmid> backup —file backup
    • Check the VCMDB type using
    • symmaskdb — sid <symmid> list database
    • Convert from type 4 to type 5
    • Symmaskdb — sid <symmid> convert —vcmdb_type 5 —file Covertfilename

To initialize VCMDB for the first time on a Symmetrix System

Within Ionix Control Center

  • Click on the Symmetrix array you are trying to  initialize the VCMDB
  • Select  Masking  then  VCMDB Management  and then initialize
  • Select a new backup and create a file name
  • Create a file name with  .sdm  extenstion
  • Click on  Activate the VCMDB
  • VCMDB backups are stored at  \home\ecc_inf\data\hostname\data\backup\symmserial\
  • Also it will be viewable within Ionix Control Center at  Systems/Symmetrix/VCMDB Backups/

With SymCLI

  • To query the VCMDB database
    • symmaskdb —sid <symmid> list database
    • To backup and init an existing VCMDB database
      • symmaskdb — sid <symmid> init —file backup

More technical deep dive coming soon on various other topics…including ACLX.


About the author

Devang Panchigar

With more than 7 Years of IT experience, Devang is currently the Director of Technology Solutions and IT Operations at Computer Data Source, Inc. Devang has held several positions in the past including Sr. Systems Engineer, Sr. Network Engineer, Technical Support Manager, Director of Storage Support & Operations. He has been responsible for creating and managing worldwide technical support teams, technology solutions team, operations management, service delivery, pre and post sales support, marketing and business planning. In his current role Devang oversees multiple aspects of the Technology Solutions Group that works with various Multinational and Fortune 500 companies providing them infrastructure services. Along with various industry certifications, Devang holds a Bachelor of Science from South Gujarat University, India and a Master of Science in Computer Science from North Carolina A&T State University.

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