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CONTAP-594566: Compression and compaction Reporting in Aggregate Data Reduction SE Ratio and System manager not showing properly

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Issue

  • When checking Compression, Compaction savings on AFF-C30 platform with Temperature-Sensitive Storage Efficiency (TSSE) enabled volumes.
  • It is shown in form of Ratio on a aggregate level and not on volume level which makes it complicated to understand how much savings are obtained.
  • System Manager reports 0 spaced saved by volume compression.
  • AFF-C30 systems achieve compression at the aggregate level now, not the volume level.
  • AFF-C30 systems use TSSE which is enabled by default on new AFF volumes.
  • All compression savings are reflected at the aggregate layer with TSSE.
  • Data compression, Data compaction and Cross volume dedupe savings are coalesced in Aggregate Data Reduction SE Ratio reported by the aggregate show-efficiency command.
  • Customers report that NetIQ should not be used for any analysis of what is happening on the array and the reports for efficiency at the aggregate level are faulty when they show 0 for the aggregate savings based on compression and compaction.
  • From AutoSupports we can see Aggregate efficiency for data aggregates if we check the Aggregate Data reduction SE Ratio.

Calculations: 
  • aggr1 Aggregate Data Reduction SE Ratio  = 1.68:1    
  • aggr2 Aggregate Data Reduction SE Ratio  = 1.47:1
  • Ratio 1.68:1 for  aggr1 ----  ratio for the aggr 1.68:1 means that 1.68 blocks are reduced to 1 block.
  • This implies that out of every 1.68 blocks, 1 block is stored, and the rest are saved.
  • To find out how much data is saved, we need to calculate the proportion of the blocks that are not stored.
  • Savings percentage, therefore is (1.68 - 1)/ 1.68 * 100 = 40.48 %
  • Similarly for the other aggregate aggr2 ratio is 1.47:1 which means that every 1.47 blocks are reduced to 1 block
  • Saving percentage, therefore is (1.47 - 1) 1.47 * 100 = 31.97%
  • Customers want to see the compression and compaction saving on aggr level separately and explicitly.
  • It would be simple for customers to just see the value of compression and compaction saving if we are saying that we are achieving saving on the aggregate level.
  • System Manager also shows compression and compaction to be achieved as 0.

 
 
 

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