Gatekeepers on "Normal" hosts

here are some of the rules for GW

1.Should be dedicated for one host only and one particular use (ECC/Solutions Enabler/WLA ...). Again, the reason is to avoid access issues.

2.Should be as small as possible to save the disk space while being still visible to the host.

Now the question how we can dedicate them for ECC or SE

I don't disagree with what SKT says here, but it doesn't quite answer the question directly.

There is no reason to assign gatekeepers to any host that does not require some kind of control or monitoring connectivity to the Symm. So, unless you have Solutions Enabler loaded you don't need Gatekeepers. And since you aren't supposed to reused gatekeepers for multiple hosts, you really don't want to put them anywhere you don't specifically need them.

Now, that being said, even hosts with SE may work without specific gatekeepers, but you don't really want to let them do that. If you DON'T give the host GKs it will use other devices masked from the Symm. This can affect your performance. So if you need SE, assign gatekeepers, and preferably make sure you define them as such using "symgate"

Just unmask it like you would any other device. A GK is just a small device used by the host for array communications. Solutions Enabler will use the smallest device available for a GK (which is why a size of 3 cylinders is usually used), but you can also define GK using the symgate command.

I now have a question. How can you remove a GK from a host that has no need for one? Thank you for any help.

Here It go......


To perform software operations on the Symmetrix, we use the low level SCSI command. To send SCSI commands to the Symmetrix, we need to open a device. We refer to the device we open as a gatekeeper. Symmetrix gatekeepers provide communication paths into the Symmetrix for external software monitoring and/or controlling the Symmetrix. There is nothing special about a gatekeeper, any host visible device can be used for this purpose. We do not actually write any data on this device, nor do we read any date from this device. It is simply a SCSI target for our special low level SCSI commands. We do perform I/O to these devices and this can interfere with applications using the same device. This is why we always configure small devices (NO data is actually stored) and map them to hosts to be used as "gatekeepers". Solutions Enabler will consider any device with 10 cylinders or less to be the preferred gatekeeper device.

Now you must have understood what is gatekeeper devices. Let me explain more about uses like how many gatekeeper you want to present host so there will be no performance impact.

A general recommendation for the number of gatekeepers for a single host with few applications running is 8. However, a common rule of thumb is a minimum of 6. For a host on which many applications running, 16 is recommended. A gatekeeper should not be mapped/masked to more than one host.
Granular Recommendation (for Solutions Enabler) :
It is hard to recommend an exact number of gatekeepers required for a single host. The number of gatekeeper's required depends on the specific host's configuration and role. This is because it directly relates to performance, therefore it is a subjective number. The following is a recommendation based upon a number of variables pertaining to that specific host. At least 2 gatekeepers for simple Solutions Enabler commands and 1 additional gatekeeper for each daemon or EMC Control Center Agent running on the host.
Granular Recommendation (for Control Center) :
¿ Two gatekeepers are required when the Storage Agent for Symmetrix is installed on the host, and two (total of four) additional gatekeepers are required when you use Symmetrix Configure commands to manage the Symmetrix system. Each Symmetrix system needs only two Symmetrix agents. The agents need to be installed on separate hosts. This is to provide for
failover when the primary agent goes down for maintenance (or failure).
¿ Common Mapping Agent and host agents do not require a gatekeeper.
¿ Note: SYMCLI scripts should not use gatekeepers assigned to ControlCenter; they should have their own.

Gatekeepers are typically 6 cylinders or 2888 KB in Size. All gatekeeper type devices should be protected by either RAID-1 or RAID-S.
Hope this will help you in deciding number of gatekeeper to assign the host.Because it is matter of performance.




Sanjeev Tanwar

Can you dedicate GK's for specific tasks ? So if a certain host has 4 device groups and you want to make sure each device group can be controlled separately no matter what happens to any of the other groups. How would you attach a dedicated GK to such a group ?

but how do you tell which group is used for which task ? Group A for ECC only, while Group B for TImefinder operation while Group C only for TMEI ?

Yes, you can assigne specific gatekeeper device for the device group using the following command

symgate -g dgname associate pd c#t#d#s2. //dgname is you device group



Sanjeev Tanwar

Yes, you can assigne specific gatekeeper device for the device group using the following command

symgate -g dgname associate pd c#t#d#s2. //dgname is you device group



Sanjeev Tanwar

I believe when you are associating the gatekeeper device with the particular group then its only dedicated for that device group only......and if you have more device group you can do the similiar process and moreover if still there are more gatkeeper device are on that host .....they can used for all other general purpose...