Unisphere for VMAX: Discrepancy in Unisphere for VMAX Write Pending Count’s graph
Summary: Discrepancy in Unisphere for VMAX Write Pending Count’s graph
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Symptoms
SRDF/A Group ## dropped due to the devices reaching the max Write Pending limit with CACA.10 error. Cache limit was set to 0xbf (74%). However, from the UNIMVAX side, there is no reading that exceeded the 75% threshold WP via Performance -> Graph -> System -> "WP Count" under "KPI Metrics".
Background:
From the array side, confirmed that SNOW dropped in that SRDF/A Group and Actual WP count at the time of the error hit the 75% WP count. However, from the Unisphere VMAX WP Count Graph shows the highest reading around 64% of the max limit at the same time.
Environment:
EMC SW: Unisphere for VMAX 8.0.2.6
Background:
From the array side, confirmed that SNOW dropped in that SRDF/A Group and Actual WP count at the time of the error hit the 75% WP count. However, from the Unisphere VMAX WP Count Graph shows the highest reading around 64% of the max limit at the same time.
Environment:
EMC SW: Unisphere for VMAX 8.0.2.6
Cause
The STP/UPV data captures the wp count at each interval so every 5 minutes.
If the WP limit was hit within that 5 minutes then dropped then we capture to "number".
This does not mean it never reached that height, it just may have not been that high when the interval to capture the stats was run.
We often see this with short sharp bursts in workload which backup in cache very quickly and then the limit is hit and then drops off, then the interval runs and everything looks great.
If the WP limit was hit within that 5 minutes then dropped then we capture to "number".
This does not mean it never reached that height, it just may have not been that high when the interval to capture the stats was run.
We often see this with short sharp bursts in workload which backup in cache very quickly and then the limit is hit and then drops off, then the interval runs and everything looks great.
Resolution
You can change the data format of the WP count chart from Average to Maximum and see the correct values.
To change the chart style, click > Chart Style (you will see this on the right top of the graph ) and select DATA Format > Maximum.
P.S, Maximum metric value will show the high water mark and should give you the high WP count reached
To change the chart style, click > Chart Style (you will see this on the right top of the graph ) and select DATA Format > Maximum.
P.S, Maximum metric value will show the high water mark and should give you the high WP count reached
Article Properties
Article Number: 000061668
Article Type: Solution
Last Modified: 01 Oct 2025
Version: 4
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