AIX

Hi Everyone,

lscfg will get the disk information by reading the VPD of that particular hdisk

I have few doubts about how Aix works, please help me to get them clear

1) How can Aix gets the disk serial number after disk assign and cfgmgr
2) Newly added disk information was added to CuVPD after running cfgmgr, who is responsible for updating the CuVPD with corresponding disk information?

I have pasted the sample hdisk information, please consider this output and help me to clear my doubts.

Code:

bash-3.2# odmget -q "name like hdisk17" CuVPD

CuVPD:
        name = "hdisk17"
        vpd_type = 0
        vpd = "*MFIBM     *TM\n\
HUS103073FL3800 *F00P3833     *RL52505151*SN004B336C*ECH17923D   *P26K5191     *Z0\n\
000004129F00013E*ZRPQQ        *Z20068*Z305289"

Many Thanks,
Sachin.

1. it gets not after cfgmgr, but during using SCSI inquiry, I suppose - The Linux SCSI programming HOWTO: Inquiry Command Example

2. nobody is responsible for updating CuVPD. Serial number of a disk can't be changed. If you change a disk, you can remove it from the system and run cfgmgr again to get new information.

* What I recall is that VPD is provided by the device (driver) via queries - as agent.kgb suggested.

* The VPD (or ODM file CuVPD (for Cu(rrent) VPD is primarily, perhaps solely, as a way to determine the firmware of a device without actually querying the device. What I also recall is when VPD status is changed (e.g., a new disk drive firmware) the VPD is updated.

** So, who is responsible? The device driver would be my simple answer.

* A related question (that you did not pose) is how does AIX keep track of a disk - is it new, or just moved within the system?

The primary means to identify a disk (volume) is to use the PVID - which is an ID that AIX assigns when the disk (aka volume) is first assigned to a volume group. There is a second attribute "unique_id" that may also be used. This value, most generally, is derived from a WWID of some kind especially for LUNs from SAN, or VSCSI.

So, a virtual (scsi) disk may not have any VPD data - as it is not physical!

As an example, my hdisk0 - it's VSCSI.

Code:

michael@x071:[/home/michael/]odmget -q name=hdisk0 CuDv

CuDv:
        name = "hdisk0"
        status = 1
        chgstatus = 2
        ddins = "scsidisk"
        location = ""
        parent = "vscsi0"
        connwhere = "810000000000"
        PdDvLn = "disk/vscsi/vdisk"

Code:

michael@x071:[/home/michael/]odmget -q name=hdisk0 CuAt

CuAt:
        name = "hdisk0"
        attribute = "unique_id"
        value = "352000c291f5ae0a75a5000000000000000005VDASD03AIXvscsi"
        type = "R"
        generic = ""
        rep = "n"
        nls_index = 0

CuAt:
        name = "hdisk0"
        attribute = "pvid"
        value = "00c291f5ae30ce0b0000000000000000"
        type = "R"
        generic = "D"
        rep = "s"
        nls_index = 11

Code:

michael@x071:[/home/michael/]odmget -q name=hdisk0 CuVPD
# no output !

Hope this helps your understanding of AIX disk administration.