Not sure why that would be, but you can verify your numbers based on the pools (provided you don't have any DSE tracks allocated).

The compression ratio for a pool is the ratio of the sum of logical used pool capacity and sum of physical pool capacity (excluding DSE tracks).

Logical pool capacity is sum of tracks used * track size of 128.

Physical pool capacity is sum of used tracks * pool track size.

You can determine the pool track size by a symdev show of a TDAT in the particular pool.  Take the sectors per track number / 2 and that is the pool track size.

Note that if a pool is empty, it will show the maximum compression ratio available for that pool. for example an empty  32K track size pool will show up as 4.0:1

If you do the math on your pools, does it match the pool report?

                       S Y M M E T R I X   P O O L S

-----------------------------------------------------------------------------

Pool         Flags  Dev              Usable       Free       Used Full   Comp

Name         PTECSL Config           Tracks     Tracks     Tracks  (%)  Ratio

------------ ------ ------------ ---------- ---------- ---------- ---- ------

DG1_F_2      TEFEEI RAID-5(3+1)    10764180    5874381    4889799   45  8.0:1

DG1_F_4      TEFEEI RAID-5(3+1)    26907300    7546631   19360669   72  4.0:1

DG1_F_5      TEFEEI RAID-5(3+1)    21527100    5897925   15629175   73  3.2:1

DG1_F_6      TEFEEI RAID-5(3+1)    10761660    3063633    7698027   72  2.7:1

DG1_F_7      TEFEEI RAID-5(3+1)     9223200    3907337    5315863   58  2.3:1

DG1_F_8      TEFEEI RAID-5(3+1)    10760400    5942159    4818241   45  2.0:1

DG1_F_9      TEFEEI RAID-5(3+1)     2391480     321331    2070149   87  1.8:1

DG1_F_F      TEFEEI RAID-5(3+1)    56465640   39125371   17340269   31  1.0:1

Total                            ---------- ---------- ---------- ---- ------

Tracks                            148800960   71678768   77122192   52  2.1:1

This is the output is the logical used track size is 77122192   and physical pool capacity is 148800960  

Using the following calculation:

For each pool, calculate logical tracks used by taking tracks used * 128.

For each pool, calculate Physical tracks used by taking tracks used * Pool_track_size

Sum The physical numbers and sum, the logical numbers.

Divide the total Logical by total physical and that is the overall compression ratio.

The above calculation on your data comes up with a ratio of 2.1:1 Exactly the number in the totals line. So I would say that the 2.1:1 is accurate based on the numbers in the pools at the time the command was run.

There is a reference table of compression ratio to pool track size in KB article : https://support.emc.com/kb/501824

I noticed that the "symcfg -sid list -srp -efficiency" will return data reduction ratio of 2.6:1.  I am not sure how this 2.6:1 is being calculated.   The array is VMAX 250FX (VMAX AFA) with PowerMax OS 5978.144.144 so in this case do we have deduplication turn on.  I thought deduplication is only available for PowerMax array with PowerMax OS so the data reduction ratio should return the same ratio in VMAX 250FX because we only have compression.   For capacity planning purpose, which compression ratio I should be used in this case.

                       STORAGE RESOURCE POOLS EFFICIENCY

Symmetrix ID  : 000297801495

--------------------------------------------------------------------------

                                 Overall  Data Reduction       VP Snapshot

Name                               Ratio   Ratio Enabled    Ratio    Ratio

-------------------------------- ------- ------- ------- -------- --------

SRP_1                              5.1:1   2.6:1     100    1.9:1    2.2:1

The number is dynamic and will be different depending on when the command is run...

Run a symcfg sync and then run both commands to do a check at the same time.