How to know _asm_stripesize for disk group

As you already know ASM supports some special file types. Today we need to pay attention for file number 1 (File Directory).

Select the group which we want to use.

SQL> select group_number, name from v$asm_diskgroup_stat;

GROUP_NUMBER NAME
------------ ------------------------------
           1 DATA
           2 OCRVT

number_kffxp=1 – (ASM file number 1 – the File Directory)

SQL> SELECT xnum_kffxp "Virtual extent",pxn_kffxp "Physical extent",au_kffxp "Allocation unit",disk_kffxp "Disk" FROM x$kffxp WHERE group_kffxp=1 and number_kffxp=1 ORDER BY 1, 2;

Virtual extent Physical extent Allocation unit       Disk
-------------- --------------- --------------- ----------
             0               0               2          0
             0               1               2         47
             0               2      4294967294      65534
             1               3               9          8
             1               4              10         26
             1               5      4294967294      65534
             2               6          372450         22
             2               7          372551         25
             2               8      4294967294      65534
             3               9          397134         20
             3              10          397328         24

We should take string which contain Virtual extent > 0. Define disk path.

SQL> SELECT disk_number, path FROM v$asm_disk_stat WHERE group_number=1 and disk_number = 22;

DISK_NUMBER
-----------
PATH
--------------------------------------------------------------------------------
         22
ORCL:T1L222

Define AU size

kfed read /dev/oracleasm/disks/T1L222 aun=0 blkn=0 |grep "ausize"
kfdhdb.ausize:                  1048576 ; 0x0bc: 0x00100000

And finally we can get information about stripe size.

kfed read /dev/oracleasm/disks/T1L222 ausz=1048576 aun=372450 blkn=0 | egrep "strpwdth|strpsz"

kfffdb.strpwdth:                      8 ; 0x04c: 0x08
kfffdb.strpsz:                       20 ; 0x04d: 0x14

kfffdb.strpsz – it’s a 2^N. This way 2^20 = 1048576 byte.

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