Can you please provide the exact answers for the below mentioned questions.
How to create gatekeeper device?
How many gatekeeper devices required per Array (DMX-4 and VMAX)
Should we mask the gatekeeper devices to any host (management host/ application server)
what is the recommended size for the gatekeeper devices
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.
Also a good reference is the CLI document available on powerlink (Chapter 10):
EMC Solutions Enabler
Symmetrix Array Management CLI PRODUCT GUIDE
Hope this helps,