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August 30, 2011

VMworld: Storage vMotion Deep Dive (VSP3255)

Speaker: Min Cai, Ali Mashtizadeh (VMware)

Agenda:
– Basics of Storage vMotion
– Use Cases
– History of vMotion
– Architectural Overview in vSphere 5
– Snapshots & Storage vMotion
– Linked Virtual Machines
– Future Roadmap

Storage vMotion
– migrate live VM to new storage
– – VM stays on same host
– – all or varied datastore targets
– – storage type independent
– – thick/thin disk support
– – RDM to VMDK conversion
– – snapshot support (5.0+)
– migration does not disturb VM
– – no downtime
– – transparent to VM
– – guaranteed success
– – minimal performance impact

Use Cases
– Storage DRS
– – storage maintenance mode
– – storage load balancing (space or performance)
– retire or migrate between arrays
– – arrays coming off of maintenance or lease cycles
– storage tiering
– – FC to iSCSI to NAS (or any mix)
– eliminate performance bottlenecks
– – load balance through LUN reconfiguration
– – seamlessly add and begin using new LUNs
– upgrade VMFS non-disruptively
– – future-proofing disk format

History: (image; coming soon)

Architectural Overview
– virtual machine’s home directory
– – config file, logs, swap file, snapshots, misc files
– virtual machine disks
– – treated differently
– I/O mirroring in ESX 5.0

Snapshots
– preserve state of VM at a specific point in time
– – config state, memory state, disk state
– snapshot components
– – descriptor file (.vmsd), config file (.vmsn), delta disk (-delta.vmdk)
– snapshot file placement
– – descriptor and config file in home (default) or SnapshotDirectory
– – delta disk in same location as the parent disk (New in vSphere 5)

Migrating VMs with Snapshots
– change datastore for the whole VM
– – all VM files and disks will be migrated to the target datastore including snapshot files
– change datastore for VM home
– – all VM files except disks will be migrated to target datastore
– – all base and delta disks will remain in source datastore
– change datastore for one or more virtual disks
– – only base and delta disks migrated to target datastore
– – no change to other VM and snapshot files

Basics of Linked Virtual Machines
– a group of VMs that share one or more disk links
– benefits:
– – reduce storage usage by sharing duplicated data using delta disks
– – enable instant deployment of large number of VMs without copying disks
– – better performance for duplicate, read intensive disks
– example use cases
– – VMware View (VDI)
– – VMware vCloud Director

Migrating Linked Virtual Machines
– move only child-most disk only
– – disk backings stay on source disk
– move all disk backings and disallow sharing
– – whole disk change will be migrated to target datastore
– move all disk backings and allow sharing
– – only unshared disk backings will be migrated over to target datastore
– – keep storage space savings on target datastore

Future
– simultaneous vMotion and Storage vMotion
– inter-VDS vMotion and Storage vMotion
– inter-vCenter vMotion and Storage vMotion
– vMotion and Storage vMotion across geographies

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