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"reallocate start" without -o option will leave the reallocation in "repeat" state

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Category:
data-ontap-8
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core
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Applies to

Data ONTAP 8.1 7-Mode

Issue

Reallocation job in the repeat state runs every day in the background without any notice and it causes an overhead on CPU and other system resources leading to unexpected performance degradation. This can be confirmed in Perfstat. For Aggregate Reallocation (free space reallocation), a scanner called block reallocation could be noticed in wafl scan status -A.

Example:

Aggregate aggr_sata1:
Scan id                   Type of scan     progress
       1                 HyA Hit Update     pvbn 17423333887 (ssd block 61964287 of 146113152) 959066 bits set
      34    active bitmap rearrangement     fbn 242925 of 536381 w/ max_chain_len 20
      47      hybrid aggregate eviction     pvbn 17485602133 (DBN 2471574 of 24352192)
     771             block reallocation     block 1249491968 of 1326454656 (94%)

Something similar is seen from wafl scan status for Volume Reallocation (used space reallocation). Another symptom in perfstat is that the Disk Read/Write throughput might be a lot higher than the user protocol Read/Write, without any internal workload to explain the gap (unaligned I/O, fragmentation, Data Protection, and Dedupe/Compression might contribute to this gap).

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