vsan: data placement€¦ · vm component 2. witness. component 1. witness. component 2. component...

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vSAN: Data PlacementDeep Dive

Adam Sweetser, VMware, Inc.Ken Werneburg, VMware, Inc.

HCI3291BU

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VMworld 2018 Content: Not for publication or distribution

Disclaimer

2©2018 VMware, Inc.

This presentation may contain product features orfunctionality that are currently under development.

This overview of new technology represents no commitment from VMware to deliver these features in any generally available product.

Features are subject to change, and must not be included in contracts, purchase orders, or sales agreements of any kind.

Technical feasibility and market demand will affect final delivery.

Pricing and packaging for any new features/functionality/technology discussed or presented, have not been determined.


‹#› 3©2018 VMware, Inc. 3

“A mind that is stretched by a new experience can never go back to its old dimensions.”

Oliver Wendell Holmes, Jr.


4©2018 VMware, Inc. 4

vSAN Datastore

What Is VMware vSAN?

Runs on any standard x86 server

Integrated into hypervisor

Pools HDD/SDD into single cluster-wide shared datastore

Easily scalable

Managed through VM storage policies

vSANvSphere



What Is VMware vSAN?

Runs on any standard x86 server

Integrated into hypervisor

Pools HDD/SDD into single cluster-wide shared datastore

Easily scalable

Managed through VM storage policies

vSAN

vSAN Datastore

vSphere


Agenda

6©2018 VMware, Inc.

Agenda

6

Objects

Data On Disk

Storage Policies

Maintenance Mode



Objects



Objects Are Pieces of VMs

Name Space – Configuration file (VMX), friendly name, and logs (vmware.log).

VMDK – Storage for the VM’s OS.

vSWP – Used during host memory contention.

Snapshot – A temporary point in time state.

Memory Snapshot – A temporary point in time of the memory state.

Default Storage Policy = One Failure to Tolerate

Name Space Component 1 Component 2

VMDK

vSWP

Snapshot

Mem Snap

VM



Objects







Name Space Mirror 1 Mirror 2

VMDK

vSWP

Snapshot

Mem Snap

Witness

VM

Component 2 Witness Component 1

Witness Component 2 Component 1

Component 1 Component 2 Witness

Component 2 Witness Witness


10©2018 VMware, Inc. 10

Objects

Need more than 50% of the components available.

Hosts Becomes Unavailable No Problem


VMDK

vSWP

Snapshot

Mem Snap

Witness

VM






11©2018 VMware, Inc. 11

Objects

Double fault - More failures than configured.

Hosts Becomes Unavailable Double Fault


VMDK

vSWP

Snapshot

Mem Snap

Witness

VM





Inaccessible Object


13©2018 VMware, Inc. 13

Data On Disks


14©2018 VMware, Inc. 14

Data On Disks is Intelligently Distributed








VMDK

vSWP

Snapshot

Mem Snap

Witness

VM






15©2018 VMware, Inc. 15

Double FaultData On Disks is Intelligently Distributed

Max of 1 cache disk per disk group.

Min of 1 capacity disk per disk group.

Max of 7 capacity disks per disk group.

Max of 5 disk groups per host.

Name Space

VMDK

vSWP

C1 C2 W

C1 C2 W

C1 C2 W

No Problem


18©2018 VMware, Inc. 18

Storage Policies


19©2018 VMware, Inc. 19

• Mirroring (RAID-1)• Erasure Coding (RAID-5/6)

Failure Tolerance Method (FTM) defines data layout approach

• FTT=1 – accessible with one failure• FTT=2 – accessible with two failures• FTT=3 – accessible with three failures

Level of Failure to Tolerate (FTT) defines level of resilience

Option with Data Protection Levels and SchemesBasic concepts around “failure tolerance method” and level of “failures to tolerate”


21

100GB VMDK


22©2018 VMware, Inc. 22

Storage Policies - RAID 0/FTT 0

Only one component.

Cannot tolerate a failure.

Space savings without redundancy.

100 GBs

Cannot Tolerate a Failure

100 GBRAID-0FTT=0

C1


23©2018 VMware, Inc. 23


Development environment

Non-critical VMs

Non-persistent VMs

Cannot Tolerate a Failure

100 GBRAID-0FTT=0

C1


24©2018 VMware, Inc. 24


Tolerates One Failure

200 GBs


100 GBRAID-1FTT=1

C1 WC2


25©2018 VMware, Inc. 25



200 GBs

Tolerates One Failure No Problem

100 GBRAID-1FTT=1

C1 WC2


26©2018 VMware, Inc. 26


Maybe?

Tolerates One FailureCouldn’t I Tolerate Two?

100 GBRAID-1FTT=1

C1 WC2


27©2018 VMware, Inc. 27


What other objects do I have?

Tolerates One FailureCouldn’t I Tolerate Two?

100 GBRAID-0FTT=1

C1 C2 W

W C1 C2


28©2018 VMware, Inc. 28


C1 = 33 GBs

C2 = 33 GBs

C3 = 33 GBs

P = 33 GBs

133 GBs in total


100 GBRAID-5FTT=1

C1 PC2 C3


29©2018 VMware, Inc. 29


C1 = 33 GBs

C2 = 33 GBs

C3 = 33 GBs

P = 33 GBs

133 GBs in total

Tolerate one failure

C1 + C2 + C3 = Parity


100 GBRAID-5FTT=1

C1 PC2 C3


30©2018 VMware, Inc. 30

C1 C4C2 C3 P2P1


C1 = 25 GBs

C2 = 25 GBs

C3 = 25 GBs

C4 = 25 GBs

P1 = 25 GBs

P2 = 25 GBs

150 GBs in total

Tolerates Two Failures

100 GBRAID-6FTT=2


31©2018 VMware, Inc. 31


C1 = 25 GBs

C2 = 25 GBs

C3 = 25 GBs

C4 = 25 GBs

P1 = 25 GBs

P2 = 25 GBs

150 GBs in total

Tolerates Two Failures

C1 C4C2 C3 P2P1

100 GBRAID-6FTT=2


32©2018 VMware, Inc. 32

Can I Change Policies?


33©2018 VMware, Inc. 33

Resync Traffic

Change from RAID 1/FTT 1 to RAID 5/FTT 1

Yes!

vSAN builds a new object on the fly

100 GBRAID-1FTT=1

C1 PC2 C3

C1 WC2

100 GBRAID-5FTT=1


35©2018 VMware, Inc. 35

Maintenance Mode


36©2018 VMware, Inc. 36

Maintenance Mode - RAID 1/FTT 1


Full Data Migration –Migrates all data, then hosts enters maintenance mode.

Ensure Accessibility –Migrates the minimum amount of components.

No Data Migration –Just goes into maintenance mode.

Maintenance Mode

100 GBRAID-1FTT=1

C1 WC2


37©2018 VMware, Inc. 37

Full Data Migration


38©2018 VMware, Inc. 38



Migrates ALL data

Fully compliant with storage policy.

Maintenance Mode – Full Data Migration

100 GBRAID-1FTT=1

C1 WC2

Resync Traffic

C2


39©2018 VMware, Inc. 39


Need at least four hosts for a full data migration.

Maintenance Mode – Full Data Migration

?100 GBRAID-1FTT=1

C1 WC2


41©2018 VMware, Inc. 41

C2


Validates we can run in a reduce state.

After 60 minutes, vSAN starts a resync.

Maintenance Mode – Ensure Accessibility Migration

100 GBRAID-1FTT=1

WC2

Resync Traffic

C1


42©2018 VMware, Inc. 42

Maintenance Mode - RAID 1/FTT 1 + RAID 0/FTT 0

Migrates FTT 0 objects first, then puts host in maintenance mode.


Maintenance Mode – Ensure Accessibility Migration

100 GBRAID-1FTT=1

WC2

Resync Traffic

C1

Resync Traffic

C2

C1C1

100 GBRAID-0FTT=0


44©2018 VMware, Inc. 44


Does not validate our state.

Does not check FTT 0 or already impacted objects.


Maintenance Mode – No Data Migration

100 GBRAID-1FTT=1

WC2

Resync Traffic

C1 C2

C1

100 GBRAID-0FTT=0

FTT 0 Object ?Inaccessible Object


47©2018 VMware, Inc. 47

Data On Disks

Max of 1 cache disk per disk group.

Min of 1 capacity disk per disk group.

Max of 7 capacity disks per disk group.

Max of 5 disk groups per host.

Name Space

VMDK

vSWP

C1 C2 W

C1 C2 W

C1 C2 W


49©2018 VMware, Inc. 49



Full Data Migration –Migrates all data, then hosts enters maintenance mode.

Ensure Accessibility –Migrates the minimum amount of components.

No Data Migration –Just goes into maintenance mode.

Maintenance Mode

100 GBRAID-1FTT=1

C1 WC2


51©2018 VMware, Inc. 51

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52©2018 VMware, Inc. 52

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