How to understand various drive or LUN names in ESXi

vmkfstools is very useful command in ESXi CLI. I issued this command on local datastore and shared datastore create on ISCSI LUN to check the speficiations.

My local datastore is created on top of one disk hence its showing extent equal to 1.

/dev/disks # vmkfstools -Ph /vmfs/volumes/esx2:local-1
VMFS-5.60 file system spanning 1 partitions.
File system label (if any): esx2:local-1
Mode: public
Capacity 39.8 GB, 38.7 GB available, file block size 1 MB, max file size 62.9 TB
UUID: 53c03384-64f1ff1a-d803-000c29e52a9d
Partitions spanned (on “lvm”):
Is Native Snapshot Capable: YES

  • In the above output mpx.vmhba1:C0:T0:L0:1 is created for local devices on the assumption that their path names are unique. They are not persistent.

While on other hand my ISCSI datastore is created on 2 LUNs hence extent value is 2.

/dev/disks # vmkfstools -Ph /vmfs/volumes/ISCSIDatastore1
VMFS-5.60 file system spanning 2 partitions.
File system label (if any): ISCSIDatastore1
Mode: public
Capacity 34.5 GB, 33.6 GB available, file block size 1 MB, max file size 62.9 TB
UUID: 53cd82fe-ade9ca7f-10af-000c29f89b93
Partitions spanned (on “lvm”):
Is Native Snapshot Capable: YES

  • UUID in both above output is unique number associated with VMFS volume upon the creation of volume. It will remain same for datastore irrespective of number of extents in it. We can have maximum of 32 extent in single datastore each with max size of 2 TB so ultimately it will becomre 64TB.
  • t10 number in output of ISCSI datastore is SCSI inquiry identifier. These are unique across all hosts and persistent.

How to check the VML numbers. Here I just grep the vml number without it we can see the detailed information related to drives.
vml is the legacy number it is unique number and persist across reboots.

/dev # esxcli storage core device list | grep -i vml
Other UIDs: vml.010002000077706f69574b2d73736d782d71317270564952545541
Other UIDs: vml.0100000000534b4a644e632d33704b392d43433748564952545541
Other UIDs: vml.0000000000766d686261313a303a30
Other UIDs: vml.0005000000766d68626133323a303a30
Other UIDs: vml.01000100003551616b676e2d735a46422d5a457634564952545541
Other UIDs: vml.01000000003030303030303030303030303030303030303031564d77617265

How to see the mapping of VML number with t10 number. Here t10.ATA.**** present the drive on which ESXi is installed.

/dev # cd /vmfs/devices/disks
/dev # ls
mpx.vmhba1:C0:T0:L0 vml.0000000000766d686261313a303a30
mpx.vmhba1:C0:T0:L0:1 vml.0000000000766d686261313a303a30:1
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001 vml.01000000003030303030303030303030303030303030303031564d77617265
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:1 vml.01000000003030303030303030303030303030303030303031564d77617265:1
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:5 vml.01000000003030303030303030303030303030303030303031564d77617265:5
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:6 vml.01000000003030303030303030303030303030303030303031564d77617265:6
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:7 vml.01000000003030303030303030303030303030303030303031564d77617265:7
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:8 vml.01000000003030303030303030303030303030303030303031564d77617265:8
t10.F405E46494C4540035B4A446E436D23307B493D234347384 vml.0100000000534b4a644e632d33704b392d43433748564952545541
t10.F405E46494C4540035B4A446E436D23307B493D234347384:1 vml.0100000000534b4a644e632d33704b392d43433748564952545541:1
t10.F405E46494C45400531516B676E6D237A56424D2A5546743 vml.01000100003551616b676e2d735a46422d5a457634564952545541
t10.F405E46494C45400531516B676E6D237A56424D2A5546743:1 vml.01000100003551616b676e2d735a46422d5a457634564952545541:1
t10.F405E46494C454007707F69675B4D23737D687D217132707 vml.010002000077706f69574b2d73736d782d71317270564952545541
t10.F405E46494C454007707F69675B4D23737D687D217132707:1 vml.010002000077706f69574b2d73736d782d71317270564952545541:1

  • One more method to see the mapping between VMFS volume UUID and t10 number. Here again extent value 1 is showing that second disk has been added to ISCSIDatastore1.

/dev/disks # esxcli storage vmfs extent list
Volume Name VMFS UUID Extent Number Device Name Partition
————— ———————————– ————- —————————————————- ———
esx2:local-1 53c03384-64f1ff1a-d803-000c29e52a9d 0 mpx.vmhba1:C0:T0:L0 1
ISCSIDatastore1 53cd82fe-ade9ca7f-10af-000c29f89b93 0 t10.F405E46494C4540035B4A446E436D23307B493D234347384 1
ISCSIDatastore1 53cd82fe-ade9ca7f-10af-000c29f89b93 1 t10.F405E46494C454007707F69675B4D23737D687D217132707 1
ISCSIDatastore2 53d6a375-e1484298-3faa-000c29e52a9d 0 t10.F405E46494C45400531516B676E6D237A56424D2A5546743 1

How to run the check on metadata? Its like Linux file system check running in 5 phases.

/dev/disks # voma -m vmfs -f check -d t10.F405E46494C4540035B4A446E436D23307B493D234347384:1
Checking if device is actively used by other hosts
Running VMFS Checker version 1.0 in check mode
Initializing LVM metadata, Basic Checks will be done
Phase 1: Checking VMFS header and resource files
Detected VMFS file system (labeled:’ISCSIDatastore1′) with UUID:53cd82fe-ade9ca7f-10af-000c29f89b93, Version 5:60
Phase 2: Checking VMFS heartbeat region
Phase 3: Checking all file descriptors.
Phase 4: Checking pathname and connectivity.
Phase 5: Checking resource reference counts.

Total Errors Found: 0

I issued df -h command just to see the mounted file system. Along with datastores I found three more vfat file system mounted.

~ # df -h
Filesystem Size Used Available Use% Mounted on
VMFS-5 39.8G 1.1G 38.7G 3% /vmfs/volumes/esx2:local-1
VMFS-5 34.5G 15.7G 18.8G 46% /vmfs/volumes/ISCSIDatastore1
VMFS-5 29.8G 961.0M 28.8G 3% /vmfs/volumes/ISCSIDatastore2
vfat 249.7M 157.8M 91.9M 63% /vmfs/volumes/5bba5c75-aadf80d0-d554-c0ac58729550
vfat 249.7M 173.2M 76.5M 69% /vmfs/volumes/f437c379-825b7d55-84bd-fce072eded7b
vfat 285.8M 192.6M 93.2M 67% /vmfs/volumes/53bf119b-f4a646b6-e139-000c29f89b93

  • Checked the information related to vfat file system I found that its for the local disk on which I have installed the ESXi. You have seen these partitions in output of “/vmfs/devices/disks”

/dev/disks # vmkfstools -Ph /vmfs/volumes/53bf119b-f4a646b6-e139-000c29f89b93
vfat-0.04 file system spanning 1 partitions.
File system label (if any):
Mode: private
Capacity 285.8 MB, 93.2 MB available, file block size 8 KB, max file size 0 bytes
UUID: 53bf119b-f4a646b6-e139-000c29f89b93
Partitions spanned (on “disks”):


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