Mapping of Physical Disk, LUNS, Cell Disks, and Grid Disks

Exadata machine comprises of compute nodes and the cell nodes. Compute nodes host the RDBMS and ASM instances along with Oracle homes, whereas the cell nodes contain data. This data is stored under several layers of abstraction starting from physical disks to LUN to cell disks, to grid disks to asm disks to asm disk groups.

From cell node, from cellcli utility you can manage physical disks, LUNs, cell disks and the grid disks.

From compute node, you can manage the asm disks and the asm disk groups.

Following is the mapping of the storage layers in the Exadata.

First comes physical disk, then LUN, then cell disk, then griddisk, and then asm disks and then asm diskgroups. There is one to one mapping between physical disk, LUN, and cell disk. so that means that for each physical disk there is one LUN, and for that LUN there is one celldisk. Then comes griddisk. Many griddisks can comprise of many cell disks. Griddisk and asm disks are synonymous with each other in exadata contest, so they are same thing. Then comes asm diskgroup, and an asm diskgroup comprises of multiple griddisks. We have three disk groups SYSTEMDG, DATA, and RECO.

List the griddisk:

CellCLI> list griddisk DATA_TT09_test1test0 detail
         name:                   DATA_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:15:39+00:00
         diskType:               HardDisk
         errorCount:             1
         id:                     00000129-000c-6341-0000-000000000000
         offset:                 32M
         size:                   430G
         status:                 active


List the celldisk of the griddisk:


CellCLI> list celldisk TT09_test1test0 detail
         name:                   TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:12:14+00:00
         deviceName:             /dev/test
         devicePartition:        /dev/test
         diskType:               HardDisk
         errorCount:             2
         freeSpace:              0
         id:                     00000129-0009-4275-0000-000000000000
         interleaving:           none
         lun:                    0_9
         raidLevel:              0
         size:                   557.859375G
         status:                 normal


List the LUN of the celldisk:

CellCLI> list lun 0_9 detail
         name:                   0_9
         cellDisk:               TT09_test1test0
         deviceName:             /dev/test
         diskType:               HardDisk
         id:                     0_9
         isSystemLun:            FALSE
         lunAutoCreate:          FALSE
         lunSize:                557.861328125G
         lunUID:                 0_9
         physicalDrives:         20:9
         raidLevel:              0
         lunWriteCacheMode:      "WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU"
         status:                 normal

List the Physical disk of the LUN:


CellCLI> list physicaldisk 20:9 detail
         name:                   20:9
         deviceId:               17
         diskType:               HardDisk
         enclosureDeviceId:      20
         errMediaCount:          23
         errOtherCount:          0
         foreignState:           false
         luns:                   0_9
         makeModel:              "TEST ST360057SSUN600G"
         physicalFirmware:       0805
         physicalInsertTime:     0000-03-24T22:10:19+00:00
         physicalInterface:      sas
         physicalSerial:         E08XLW
         physicalSize:           558.9109999993816G
         slotNumber:             9
         status:                 normal


There can be M:M relationship between celldisks and the griddisk, but in following, there is 1:M relationship between celldisk and griddisks.

List griddisks in one celldisk:

CellCLI> list griddisk where cellDisk like 'TT09_test1test0'
         DATA_TT09_test1test0         active
         RECO_TT09_test1test0         active
         SYSTEMDG_TT09_test1test0     active

List griddisks in one celldisk (in detail with wild card):

CellCLI> list griddisk where cellDisk like 'TT09.*' detail
         name:                   DATA_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:15:39+00:00
         diskType:               HardDisk
         errorCount:             1
         id:                     00000129-000c-6341-0000-000000000000
         offset:                 32M
         size:                   430G
         status:                 active

         name:                   RECO_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:15:55+00:00
         diskType:               HardDisk
         errorCount:             1
         id:                     00000129-000c-a1d6-0000-000000000000
         offset:                 430.046875G
         size:                   98.6875G
         status:                 active

         name:                   SYSTEMDG_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:13:02+00:00
         diskType:               HardDisk
         errorCount:             0
         id:                     00000129-0009-fd52-0000-000000000000
         offset:                 528.734375G
         size:                   29.125G
         status:                 active



Listing that a griddisk only belongs to one celldisk in this case:


CellCLI> list griddisk DATA_TT09_test1test0 detail
         name:                   DATA_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:15:39+00:00
         diskType:               HardDisk
         errorCount:             1
         id:                     00000129-000c-6341-0000-000000000000
         offset:                 32M
         size:                   430G
         status:                 active

CellCLI> list griddisk RECO_TT09_test1test0 detail
         name:                   RECO_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:15:55+00:00
         diskType:               HardDisk
         errorCount:             1
         id:                     00000129-000c-a1d6-0000-000000000000
         offset:                 430.046875G
         size:                   98.6875G
         status:                 active

CellCLI> list griddisk SYSTEMDG_TT09_test1test0 detail
         name:                   SYSTEMDG_TT09_test1test0
         availableTo:
         cellDisk:               TT09_test1test0
         comment:
         creationTime:           0000-07-14T02:13:02+00:00
         diskType:               HardDisk
         errorCount:             0
         id:                     00000129-0009-fd52-0000-000000000000
         offset:                 528.734375G
         size:                   29.125G
         status:                 active