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ASA has a larger Aggregate size for ONTAP 9.8 and later

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Applies to

  • All SAN Array (ASA)
  • ONTAP 9.8

Issue

Two aggregates have the same disk type, the same number of RAID group, RAID group type, and the same number of disks in each RAID group, but with different aggregate size.

Example: 

  • Cluster1: ONTAP 9.8P10; Cluster2: ONTAP 9.7P17
  • Aggr1 and aggr2 each has 42 disks (38 excluding parity) with usable size 33,629,468 MB (38 disks *884986 MB/disk), but has different aggregate size.

cluster1::> node run -node cluster1_nodeA -command sysconfig -r
Aggregate aggr1 (online, raid_dp) (block checksums)
  Plex /aggr1/plex0 (online, normal, active, pool0)
    RAID group /aggr1/plex0/rg0 (normal, block checksums)
      RAID Disk Device          HA  SHELF BAY CHAN Pool Type  RPM  Used (MB/blks)    Phys (MB/blks)
      --------- ------          ------------- ---- ---- ---- ----- --------------    --------------
      dparity   e3b.00.3.0P1    e3b   0   0          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      parity    e3b.01.3.0P1    e3b   1   0          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3a.00.0.6P1    e3a   0   6          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.01.3.6P1    e3b   1   6          0 SSD-NVM   N/A 884986/226556480  884994/226558528
    ......
    RAID group /aggr1/plex0/rg1 (normal, block checksums)
      RAID Disk Device          HA  SHELF BAY CHAN Pool Type  RPM  Used (MB/blks)    Phys (MB/blks)
      --------- ------          ------------- ---- ---- ---- ----- --------------    --------------
      dparity   e3a.00.0.12P1   e3a   0   12         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      parity    e3b.01.1.12P1   e3b   1   12         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3a.00.0.18P1   e3a   0   18         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.01.3.16P1   e3b   1   16         0 SSD-NVM   N/A 884986/226556480  884994/226558528

cluster2::*> node run -node cluster2_nodeA -command sysconfig -r
Aggregate aggr2 (online, raid_dp) (block checksums)
  Plex /aggr2/plex0 (online, normal, active, pool0)
    RAID group /aggr2/plex0/rg0 (normal, block checksums)
      RAID Disk Device          HA  SHELF BAY CHAN Pool Type  RPM  Used (MB/blks)    Phys (MB/blks)
      --------- ------          ------------- ---- ---- ---- ----- --------------    --------------
      dparity   e3b.00.1.8P2    e3b   0   8          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      parity    e3b.01.3.7P2    e3b   1   7          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.00.1.1P2    e3b   0   1          0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.01.1.1P2    e3b   1   1          0 SSD-NVM   N/A 884986/226556480  884994/226558528
    ......
    RAID group /aggr2/plex0/rg1 (normal, block checksums)
      RAID Disk Device          HA  SHELF BAY CHAN Pool Type  RPM  Used (MB/blks)    Phys (MB/blks)
      --------- ------          ------------- ---- ---- ---- ----- --------------    --------------
      dparity   e3a.00.0.20P2   e3a   0   20         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      parity    e3b.01.1.19P2   e3b   1   19         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.00.3.13P2   e3b   0   13         0 SSD-NVM   N/A 884986/226556480  884994/226558528
      data      e3b.01.1.13P2   e3b   1   13         0 SSD-NVM   N/A 884986/226556480  884994/226558528

  • Aggr1 have 28.86TB total size while aggr2 have 30.47TB

cluster1::> aggr show -fields diskcount,raidgroups,raidtype,size
aggregate            diskcount raidgroups                                raidtype size
-------------------- --------- ----------------------------------------- -------- ------
aggr1                42        "/aggr3/plex0/rg0 (block)","/aggr1/plex0/rg1 (block)"
                                                                         raid_dp  28.86TB

cluster2::*> aggr show -fields diskcount,raidgroups,raidtype,size
aggregate            diskcount raidgroups                                raidtype size
-------------------- --------- ----------------------------------------- -------- ------
aggr2                42        "/aggr2/plex0/rg0 (block)","/aggr2/plex0/rg1 (block)"
                                                                         raid_dp  30.47TB

  • The storage aggregate show command displays different wafl reserve percent on aggr1 and aggr2.

cluster1::> aggr show -fields wafl-reserve-percent
aggregate            wafl-reserve-percent
-------------------- --------------------
aggr1                10%

cluster2::> aggr show -fields wafl-reserve-percent
aggregate            wafl-reserve-percent
-------------------- --------------------
aggr2                5%

  • Calculate the aggregate size.

Aggr1: 33,629,468 MB * 0.90 (10% for wafl reserve)=30,266,521.2 MB=28.86 TB

Aggr2: 33,629,468 MB * 0.95 (5% for wafl reserve)=31,947,994.6 MB=30.47 TB

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