3PAR CPG's Growth Increment and Growth Limit

[kisalipa]

Hi Friends,

I am trying to understand on what exactly is Growth Increment on CPG and why is it necessary? What if I set it as NONE, what happens.

From what I understood, is as the Volume data occupancy happens, in advance the LD's are created by system, where in the growth increments come into picture. Lets say for a 2-node 3-par, the default increments are in multiples of 16GB. But I assume this is applicable only in case of TPVV, since FPVV has already dedicated LD's created and exported to user. Is my understanding correct? What happens if the Growth increment is disabled?

What is the difference between Volume Growth limit and CPG growth limit? Is growth limit applicable only in case of TPVV existing in CPG?

Thanks in Advance!!!

[Sheldon Smith]

First, read the HPE 3PAR StoreServ Storage Concepts Guide, especially the section on "Growth Increments, Warnings, and Limits". Just because a setting exists is no reason to change it.

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Pathologically setting limits has been a way to test SNMP and/or local email alerts for some time now.

Summary: Customers wishing to test their notification (SNMP and/or local email) setup can create a critical alert via a createcpg CLI command. The CPG is created with an allocation limit of 1G. Since the minimum growth of a CPG is 8G, the CPG grows to 1G in size and immediately reaches the allocation limit. Following the alert testing, the CPG, corresponding LDs and alert can be removed.

First check the system for any outstanding alerts:
3PAR cli% showalert
See if the list is either empty, or any alerts have been "resolved by system".

Then: Create the CPG with a 1GB growth limit:
createcpg -sdgl 1g test_alert_cpg

However for this CPG to grow, the customer would also have to create a VV with the same size as the CPG. The CPG will then reach its allocation limit. We just need to create a minimal VV:
createvv test_alert_cpg test_alert_vv 1g

An alert will then be triggered:
3PAR cli% showalert
State : New
Severity : Critical
Type : CPG growth limit
Message : CPG test_alert_cpg SD space has reached allocation limit ...

After the testing has been verified the customer can remove the VV by issuing the following command:
removevv -f test_alert_vv

and remove the remove the CPG by issuing:
removecpg -f test_alert_cpg