How to read a ASM Stamped disk to find voting disk availability without asm started

Having the voting disk in ASM is a clusterware/database 11gr2 (11.2.0.1) feature. The first time I heard about it, it got me thinking: the clusterware needs to up before the ASM instance can start, because ASM relies on the clusterware for detecting machine and cluster problems. But: ASM needs to be started to be able to find files inside ASM. Classic chicken-egg problem…

So how does the clusterware find the voting disk when it is starting? ASM is not up at that time, so it can not ask the ASM instance.

What the clusterware does, is query the diskheaders of the ASM disks. In the (11gr2) ASM disk header, there’s room to tell if, and where the voting disk is present on that disk:

C:\Users\farif>kfed read \\.\ORCLDISKDATANEWSAN0

kfbh.endian:                          1 ; 0x000: 0x01

kfbh.hard:                          130 ; 0x001: 0x82

kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD

kfbh.datfmt:                          1 ; 0x003: 0x01

kfbh.block.blk:                       0 ; 0x004: blk=0

kfbh.block.obj:              2147483648 ; 0x008: disk=0

kfbh.check:                  2894233388 ; 0x00c: 0xac827f2c

kfbh.fcn.base:                   760337 ; 0x010: 0x000b9a11

kfbh.fcn.wrap:                        0 ; 0x014: 0x00000000

kfbh.spare1:                          0 ; 0x018: 0x00000000

kfbh.spare2:                          0 ; 0x01c: 0x00000000

kfdhdb.driver.provstr:ORCLDISKDATANEWSAN0 ; 0x000: length=19

kfdhdb.driver.reserved[0]:   1096040772 ; 0x008: 0x41544144

kfdhdb.driver.reserved[1]:   1398228302 ; 0x00c: 0x5357454e

kfdhdb.driver.reserved[2]:      3165761 ; 0x010: 0x00304e41

kfdhdb.driver.reserved[3]:            0 ; 0x014: 0x00000000

kfdhdb.driver.reserved[4]:            0 ; 0x018: 0x00000000

kfdhdb.driver.reserved[5]:            0 ; 0x01c: 0x00000000

kfdhdb.compat:                186646528 ; 0x020: 0x0b200000

kfdhdb.dsknum:                        0 ; 0x024: 0x0000

kfdhdb.grptyp:                        1 ; 0x026: KFDGTP_EXTERNAL

kfdhdb.hdrsts:                        3 ; 0x027: KFDHDR_MEMBER

kfdhdb.dskname:              DGDUP_0000 ; 0x028: length=10

kfdhdb.grpname:                   DGDUP ; 0x048: length=5

kfdhdb.fgname:               DGDUP_0000 ; 0x068: length=10

kfdhdb.capname:                         ; 0x088: length=0

kfdhdb.crestmp.hi:             32969165 ; 0x0a8: HOUR=0xd DAYS=0xe MNTH=0x4 YEAR=0x7dc

kfdhdb.crestmp.lo:           3613329408 ; 0x0ac: USEC=0x0 MSEC=0x3c2 SECS=0x35 MINS=0x35

kfdhdb.mntstmp.hi:             33001418 ; 0x0b0: HOUR=0xa DAYS=0x1e MNTH=0x3 YEAR=0x7de

kfdhdb.mntstmp.lo:           2117023744 ; 0x0b4: USEC=0x0 MSEC=0x3ce SECS=0x22 MINS=0x1f

kfdhdb.secsize:                     512 ; 0x0b8: 0x0200

kfdhdb.blksize:                    4096 ; 0x0ba: 0x1000

kfdhdb.ausize:                  1048576 ; 0x0bc: 0x00100000

kfdhdb.mfact:                    113792 ; 0x0c0: 0x0001bc80

kfdhdb.dsksize:                  204800 ; 0x0c4: 0x00032000

kfdhdb.pmcnt:                         3 ; 0x0c8: 0x00000003

kfdhdb.fstlocn:                       1 ; 0x0cc: 0x00000001

kfdhdb.altlocn:                       2 ; 0x0d0: 0x00000002

kfdhdb.f1b1locn:                      2 ; 0x0d4: 0x00000002

kfdhdb.redomirrors[0]:                0 ; 0x0d8: 0x0000

kfdhdb.redomirrors[1]:                0 ; 0x0da: 0x0000

kfdhdb.redomirrors[2]:                0 ; 0x0dc: 0x0000

kfdhdb.redomirrors[3]:                0 ; 0x0de: 0x0000

kfdhdb.dbcompat:              168820736 ; 0x0e0: 0x0a100000

kfdhdb.grpstmp.hi:             32969165 ; 0x0e4: HOUR=0xd DAYS=0xe MNTH=0x4 YEAR=0x7dc

kfdhdb.grpstmp.lo:           3612037120 ; 0x0e8: USEC=0x0 MSEC=0x2d4 SECS=0x34 MINS=0x35

kfdhdb.vfstart:                     128 ; 0x0ec: 0x00000080

kfdhdb.vfend:                       160 ; 0x0f0: 0x000000a0

kfdhdb.spfile:                        0 ; 0x0f4: 0x00000000

kfdhdb.spfflg:                        0 ; 0x0f8: 0x00000000

kfdhdb.ub4spare[0]:                   0 ; 0x0fc: 0x00000000

kfdhdb.ub4spare[1]:                   0 ; 0x100: 0x00000000

kfdhdb.ub4spare[2]:                   0 ; 0x104: 0x00000000

kfdhdb.ub4spare[3]:                   0 ; 0x108: 0x00000000

kfdhdb.ub4spare[4]:                   0 ; 0x10c: 0x00000000

kfdhdb.ub4spare[5]:                   0 ; 0x110: 0x00000000

kfdhdb.ub4spare[6]:                   0 ; 0x114: 0x00000000

kfdhdb.ub4spare[7]:                   0 ; 0x118: 0x00000000

kfdhdb.ub4spare[8]:                   0 ; 0x11c: 0x00000000

kfdhdb.ub4spare[9]:                   0 ; 0x120: 0x00000000

kfdhdb.ub4spare[10]:                  0 ; 0x124: 0x00000000

kfdhdb.ub4spare[11]:                  0 ; 0x128: 0x00000000

kfdhdb.ub4spare[12]:                  0 ; 0x12c: 0x00000000

kfdhdb.ub4spare[13]:                  0 ; 0x130: 0x00000000

kfdhdb.ub4spare[14]:                  0 ; 0x134: 0x00000000

kfdhdb.ub4spare[15]:                  0 ; 0x138: 0x00000000

kfdhdb.ub4spare[16]:                  0 ; 0x13c: 0x00000000

kfdhdb.ub4spare[17]:                  0 ; 0x140: 0x00000000

kfdhdb.ub4spare[18]:                  0 ; 0x144: 0x00000000

kfdhdb.ub4spare[19]:                  0 ; 0x148: 0x00000000

kfdhdb.ub4spare[20]:                  0 ; 0x14c: 0x00000000

kfdhdb.ub4spare[21]:                  0 ; 0x150: 0x00000000

kfdhdb.ub4spare[22]:                  0 ; 0x154: 0x00000000

kfdhdb.ub4spare[23]:                  0 ; 0x158: 0x00000000

kfdhdb.ub4spare[24]:                  0 ; 0x15c: 0x00000000

kfdhdb.ub4spare[25]:                  0 ; 0x160: 0x00000000

kfdhdb.ub4spare[26]:                  0 ; 0x164: 0x00000000

kfdhdb.ub4spare[27]:                  0 ; 0x168: 0x00000000

kfdhdb.ub4spare[28]:                  0 ; 0x16c: 0x00000000

kfdhdb.ub4spare[29]:                  0 ; 0x170: 0x00000000

kfdhdb.ub4spare[30]:                  0 ; 0x174: 0x00000000

kfdhdb.ub4spare[31]:                  0 ; 0x178: 0x00000000

kfdhdb.ub4spare[32]:                  0 ; 0x17c: 0x00000000

kfdhdb.ub4spare[33]:                  0 ; 0x180: 0x00000000

kfdhdb.ub4spare[34]:                  0 ; 0x184: 0x00000000

kfdhdb.ub4spare[35]:                  0 ; 0x188: 0x00000000

kfdhdb.ub4spare[36]:                  0 ; 0x18c: 0x00000000

kfdhdb.ub4spare[37]:                  0 ; 0x190: 0x00000000

kfdhdb.ub4spare[38]:                  0 ; 0x194: 0x00000000

kfdhdb.ub4spare[39]:                  0 ; 0x198: 0x00000000

kfdhdb.ub4spare[40]:                  0 ; 0x19c: 0x00000000

kfdhdb.ub4spare[41]:                  0 ; 0x1a0: 0x00000000

kfdhdb.ub4spare[42]:                  0 ; 0x1a4: 0x00000000

kfdhdb.ub4spare[43]:                  0 ; 0x1a8: 0x00000000

kfdhdb.ub4spare[44]:                  0 ; 0x1ac: 0x00000000

kfdhdb.ub4spare[45]:                  0 ; 0x1b0: 0x00000000

kfdhdb.ub4spare[46]:                  0 ; 0x1b4: 0x00000000

kfdhdb.ub4spare[47]:                  0 ; 0x1b8: 0x00000000

kfdhdb.ub4spare[48]:                  0 ; 0x1bc: 0x00000000

kfdhdb.ub4spare[49]:                  0 ; 0x1c0: 0x00000000

kfdhdb.ub4spare[50]:                  0 ; 0x1c4: 0x00000000

kfdhdb.ub4spare[51]:                  0 ; 0x1c8: 0x00000000

kfdhdb.ub4spare[52]:                  0 ; 0x1cc: 0x00000000

kfdhdb.ub4spare[53]:                  0 ; 0x1d0: 0x00000000

kfdhdb.acdb.aba.seq:                  0 ; 0x1d4: 0x00000000

kfdhdb.acdb.aba.blk:                  0 ; 0x1d8: 0x00000000

kfdhdb.acdb.ents:                     0 ; 0x1dc: 0x0000

kfdhdb.acdb.ub2spare:                 0 ; 0x1de: 0x0000

kfdhdb.vfstart tells the begin allocation unit offset of the voting disk, kfdhdb.vfend tells the end offset.