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ONTAP 9 - Per Aggregate CP

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Applies to

  • ONTAP 9

Answer

  • ONTAP 9 has performance enhancements to lessen the impact of consistency points.
    • Rather than processing a single consistency point for all aggregates at the same time (Global), ONTAP 9 has the functionality to allow each aggregate to commit CPs independently of one another.
  • It is still possible for Back to Back consistency points to occur, however, the negative performance of one aggregate should not affect other aggregates.
    • This is important to keep in mind when troubleshooting performance on a cluster running ONTAP 9.
  • With ONTAP 9 and Per-Aggregate CP's, the CP information in sysstat has changed.
    • Example (some columns removed for readability):
cluster::*> node run -node node_1 sysstat -x 1
 CPU   Total     Net   kB/s    Disk   kB/s     CP           CP_Ty               CP_Ph       Disk     FCP   kB/s   iSCSI   kB/s
                  in    out    read  write   time  [T--H--F--N--B--O--#--:]  [n--v--p--f]   util      in    out      in    out
  3%      13      56     56    3300   27760   97%   1--0--0--0--0--0--0--0    0--0--0--1     65%       0      0       0      0
  3%       0      55     55      30     240   11%   0--0--0--0--0--0--0--0    0--0--0--0      9%       0      0       0      0
  4%       8      66     64      12       0    0%   0--0--0--0--0--0--0--0    0--0--0--0      0%       0      0       0      0
  8%       0      50     50       0      12    0%   0--0--0--0--0--0--0--0    0--0--0--0      1%       0      0       0      0
  • Instead of displaying individual CP's, a summary of CP's is now displayed:

         CP_Ty               CP_Ph    
[T--H--F--N--B--O--#--:]  [n--v--p--f]

  • The "CP_Ty" columns now display the number of aggregates that had a CP triggered (or continuing) due to the following reasons:

CP_Ty

 Definition
T CP caused by timer
H CP caused by high water mark; the amount of modified data in the storage system's memory cache is high enough that it
is ideal to start a CP to force it out to disk
F CP caused by full NVLog; the amount of logged data in the storage system's NVRAM pool is high enough that it is ideal
to start a CP to force it out to disk
N CP caused by the NV Log reaching a maximum number of entries
B Back to back CP
O All other types of CP
# Continuation of CP from the previous interval and the storage system has determined it needs to commit the current data to
disk (a watermark of some sort has been reached), so that the next CP will be of type B
: Continuation of CP from the previous interval
  • The "CP_Ph" column represents the number of aggregates in the following phases:

CP_Ph

 Definition
n Processing normal files
v Flushing modified superblock to the disk
p All other file processing
f Flushing modified data to disk

 

Additional Information

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