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Alert 194: CPG Grown With Degraded Parameters (Degraded)

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Alert 194: CPG Grown With Degraded Parameters (Degraded)

Dear Sir:

Customer face alert message Alert 194: CPG Grown With Degraded Parameters (Degraded) ,

would like to modify ” physical disk filter from “-ssz 12 -ha cage -p -devtype SSD -mg 3-5” to “-ssz 12 -ha cage -p -devtype SSD -mg 3-6 “ ,  would appreciate it if you have any advice for that  ,is there any potential risk for the change ?



Re: Alert 194: CPG Grown With Degraded Parameters (Degraded)

There are details missing like what is the 3PAR model, Inform OS version running, How many nodes present in the system etc

I understand earlier one of the CPG parameter was "-ssz 12 -ha cage -p -devtype SSD -mg 3-5" which means high availability configured as Cage and set size is 12 but not sure what is the RAID defined. By default it may be RAID 6. Now question is how many cage present in the system and as you have mentioned "-mg" switch so every cage these drive position only will be involved at the time of LD creation. Not sure why specific drive position only you have configured. Earlier drives were getting selected from 3-5 and now you want to select 3-6.

You can check the best practice gudie to get more ideas,


"Solid-state drive CPGs
Consider the following best practices when creating SSD CPGs:
• SSD CPGs should be configured with RAID 6 with the default set size. This will yield a superior performance/capacity ratio and 6+2 on systems that have enough SSDs to support 6+2, for larger systems R6 14+2 gives the best capacity / performance mix.
• The growth increment should be set to the minimum value, which is 8 GB per node pair.
– On two-node systems, set the value to 8 GB.
– On four-node systems, set the value to 16 GB.
– On six-node systems, set the value to 24 GB.
– On eight-node systems, set the value to 32 GB.
To set the CPG growth increment to a lower value than the default, check the Show advanced option box.
• Availability should be left to “cage level” (the default option) if the system’s configuration allows for it. If not, it should be set to “magazine level” availability. You can change this by checking the Advanced options box in the SSMC. "



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