Gatekeeper devices

Hello Lakshman,

    Also a good reference is the CLI document available on powerlink (Chapter 10):

EMC Solutions Enabler
Symmetrix Array Management CLI PRODUCT GUIDE
P/N 300-002-939
REV A03

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/Technical_Documentation/300-002-939_a08.pdf?mtcs=ZXZlbnRUeXBlPUttQ2xpY2tDb250ZW50RXZlbnQsZG9jdW1lbnRJZD0wOTAxNDA2NjgwNGUzMGZhLGRvY3VtZW50VHlwZT1wZGYsbmF2ZU5vZGU9MGIwMTQwNjY4MDRlMjY4Nl9Hcmlk

Hope this helps,

   Nollaig

lakshman,

if you search Gatekeeper in the forum you will get many threads which covers all your question.

just check the primus as well emc180055, below are from the same primus solutions.

What are Gatekeepers?
As the size of Symmetrix  arrays increase, to effectively monitor and manage an array, more and  more data must be exchanged between the ControlCenter Agents responsible  for the Symmetrix arrays (Symmetrix / SDM) and the Symmetrix arrays  themselves.  Gatekeepers are normal Symmetrix devices used to facilitate  this data exchange.

Where do I need Gatekeepers?
Gatekeepers should  be assigned per attached management host.  A management host is any host  running a copy of Solutions Enabler intended to be used for Symmetrix  monitoring and management.  Since Solutions Enabler does more than just  monitor Symmetrix Arrays, not all hosts with Solutions Enabler will need  gatekeepers assigned.

Per management host, how many Gatekeepers do I need?
The minimum number of Gatekeepers supported by EMC are 5.  When less  than 5 Gatekeepers are available to a management host, both SMC and the  ControlCenter console will generate alerts stating that fewer than 5  gatekeepers are present. Six (6) Gatekeepers is sufficient to satisfy  the communication requirements for Symmetrix Management Console (SMC)  and ControlCenter’s Symmetrix Management and SDM agents.  When planning  the storage management environment where ControlCenter and SMC  components reside together on the same host, only six (6) gatekeepers  are required per Symmetrix management host.  Assigning additional  gatekeepers does not provide any significant benefit.

From the point-of-view of the Symmetrix, how many Gatekeepers do I need to create?
First,  count the number of hosts that will be used to actively manage the  Symmetrix.  This is typically a very small number.  Take this number,  and multiply it by 6.  That is the total number of Gatekeepers that  should be created on the Symmetrix.  For example, in an environment with  4 management hosts, a total of 24 Gatekeepers should be created.  Each  unique Gatekeeper should only be assigned to one FA port, and masked to  only one host HBA.  This ensures Gatekeepers are not shared across  multiple hosts, which could reduce the management performance.

How do I create Gatekeeper devices?
Create  Gatekeeper devices like any other device, but keep the size to 2880 KB.   See the ControlCenter Online Help for instructions.  Once created, map  the devices to the appropriate Symmetrix front-end port, then mask the  devices to the appropriate host HBAs.

How do Gatekeepers assist in communicating with Symmetrix arrays?
Communication  with Symmetrix arrays occurs by sending syscalls to the array along the  same channels used for normal storage I/O.  For Open Systems hosts,  this means we send monitoring and management commands over SCSI protocol  (SCSI pass-through commands) to Symmetrix devices visible to that  host.  As long as devices (LUNs) from an array are visible to a host, a  Symmetrix Agent installed on that host can actively manage that  Symmetrix array.

There can be performance issues, however, if we are using the same  devices for both I/O (read-write) and management.  Sending one type of  command can cause the other to block until the outstanding commands are  completed.  To get around this problem, you can present special devices  to the host called Gatekeepers.

Gatekeepers are normal Symmetrix devices (of any type), that have a  very small size.  Most Gatekeeper devices are below 3 MB in size.  This  makes it very difficult to accidentally perform I/O operations to the  device (since there is practically no usable space on the  device), ensuring the device is only used for monitoring and management  commands.  ControlCenter, through Solutions Enabler, automatically  recognizes these devices as Gatekeepers, and will prefer these devices  when performing management functions.

Each Gatekeeper can handle a certain amount of traffic before it  becomes locked.  Once outstanding commands are completed, the Gatekeeper  will become unlocked and new commands can be processed.  In situations  where many commands are being sent simultaneously (like in the case of  Symmetrix and SDM Agents), multiple Gatekeepers are needed to ensure all  commands are processed in a speedy manner.