ITEM: AC5980L

Maximum Physical Partition and filesystem size, PP's in LV

Question:


   Env: 3.2.5 and 4.1
   Desc: Customer wanted to know the maximum Physical Partition
        size, maximum number of Physical Partitions per Logical
        volume and maximum filesystem size  under AIX 3.2.5
        and AIX 4.1
   Action:
                        3.2.5           4.1
        ------------------------------------
        PP size         256MB           256MB
        PP's in LV (see note)
                        65535           65535
        Filesystem size 2 GB            64 GB

        AIX 3.2.5 used 32 bit signed integers for addressing
        AIX 4.1 uses 64 bit long long variables for addressing

        note:
                The limits on PP is actually a hard coded limit due to the
        fact that integers are used to represent this field.  The actual
        limit that can be allocated is 32512 PP's per LV.  This is found
        by knowing that we can have 32 PV's per VG and since one LV can
        span the entire VG and you can have max of 1016 PP's per PV.

        That is:
                32 Pv/VG * 1VG/1LV * 1016 PP/PV = 32512 PP/LV   

        But since AIX can only address 2GB filesystems under 3.2.5 or 4Gb
        filesystems under 4.1 these logical volumes would have to be 
        accessed as raw logical volumes.

        Also, this would allow a maximum of 8.52e+12 bytes in one VG.
                32 PV/VG * 1016 PP/PV * 256MB/PP = 8.522e+12 MB

        Sources:
                Filesystem limits for AIX 4.1: All About AIX 4.1 pg 91
                /usr/include/lvm.h for:
                        LVM_MAXPPS   Max \# of PP's
                        LVM_MAXLPS   Max \# of LP's
                        LVM_MAXPVS   Max \# of PV's
   Next Action:
   Test Case:



Support Line: Maximum Physical Partition and filesystem size, PP's in LV ITEM: AC5980L

Dated: April 1997 Category: N/A

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