The document provides a comprehensive overview of VMware's vSphere Flash Read Cache, highlighting its role in enhancing application performance by utilizing flash storage in a software-defined data center. It details configuration options, compatibility with vSphere features, and performance monitoring metrics critical for optimizing virtual machine workloads. The solution is presented as agentless and user-friendly, with support for various flash devices and configurations tailored to improve read I/O performance in virtual environments.

1. vSphere Flash Read Cache Technical Overview
Kiran Madnani, VMware
Rawlinson Rivera, VMware
STO5588
#STO5588

2. 2
Agenda
 VMware and SDS
 The importance of Flash
 vSphere Platform – Flash Functions and Considerations
 What is vSphere Flash Read Cache
 vSphere Flash Read Cache Configuration Options
 vSphere Flash Read Cache vSphere Features
Interoperability
 Performance and Monitoring
 Packaging
 Summary

3. 3
Software-Defined
Data Center
Software-Defined
Storage
SDDC | SDS
All infrastructure is virtualized
and delivered as a service, and
the control of this data center is
entirely automated by software.
Heterogeneous storage resources
are abstracted into logical pools,
consumed and managed through
app-centric policy-based
automation

4. 5
VMware Approach To Software-Defined Storage
vSphere
App-centric
Data Services
Policy-Driven Control Plane
Virtual Data Plane
External storage Pool
Converged Infrastructure Pool
Backup
VM Storage Policy
 Capacity
 Performance
 Availability
 …
BLOB

5. 6
The Importance of Flash

6. 7
The Importance of Flash Based Devices
Moore’s Law will continue to improve
CPU performance
Disk drive performance remains flat.Time
Performance
FLASH

7. 8
vSphere Platform – Flash
Functions and Considerations

8. 9
Leveraging Flash Based Devices in vSphere
Key Feature vSphere Functionality Considerations
• Must be simple to configure, and manage
• Work with any flash based device – SAS, SATA, or PCIe
• Support all types of vSphere datastore – VMFS and NFS
• Must be agentless and transparent to the guess OS/App
• Support granular allocation – not all disks are the same!
• Significantly improve application performance
• Seamlessly work with other vSphere features:
• vMotion
• DRS,
• HA

9. 10
vSphere Flash Read Cache: Accelerate VM Performance
• Pools multiple flash devices as a resource
• Hypervisor-based caching solution
• Per-VMDK granular allocation
• Compatible with vMotion, DRS & HA
• VMFS and NFS data stores supported
• Supports PCIe, SAS, SATA interfaces
• Accelerates performance for business
critical applications
• Enables efficient use of server flash in
virtual environments
• Fully transparent read-caching – no host
agents or application changes
Overview
Benefits
vSphere
SAN/NAS
CPU Pool Memory PoolFlash Pool
New
Accelerate
performance

10. 11
Components of the solution
Virtual Flash Resource
vSphere Flash Read Cache
Pools multiple flash
devices to present a
single resource;
seamlessly integrates
with vSphere capabilities
Provides per-VMDK
caching
vSphere

11. 12
vSphere Flash Read Cache
Configuration Options

12. 13
Configure Virtual Flash Resource
• vSphere Admin configures Virtual Flash Resource by combining local flash
devices on a single or across multiple hosts

13. 14
Configure vSphere Flash Read Cache for VMDKs
• vSphere Admin configures virtual machines to use vSphere Flash Read
Cache for VMDKs.

14. 15
Use of Virtual Flash Resource
Virtual Flash Resource
VMDK1 without
vFRC
VMDK2 with
vFRC
vSphere Flash Read Cache
SSD
vSphere
SSD
• VMs transparently use the Virtual Flash Resource without modifying
any of the virtual machines operations

15. 16
vSphere Flash Read Cache in Action – vMotion, DRS, HA
Virtual Flash Resource
vSphere Flash Read Cache vSphere Flash Read Cache vSphere Flash Read Cache
Flash
Resource
Caching
Module

16. 17
vSphere Flash Read Cache
and
vSphere Features Interoperability

17. 18
vSphere Flash Read Cache – vMotion Options
vMotion workflows have been modified to include a new set of checkpoints
applicable to the validation of cache contents.
Advanced setting allow the selection of cache migration setting for individual VMDKs

18. 19
vSphere Flash Read Cache – vMotion Options
vMotion
vFRC vFRC
XvMotion
vMotion Migration
 if migrateCache is true, in
order to effectively transfer
the Cache content from
source to the destination
host, vMotion migration
process is converted into
XvMotion.
VC compatibility check
 Sufficient Virtual Flash
Resource on destination host

19. 20
vSphere Flash Read Cache – vMotion Options
Migrate Rebuild
Always
migrate the
cache contents
Do not
migrate the
cache contents
Migration Setting
Virtual Flash Cache State

20. 21
vSphere Flash Read Cache – SvMotion
vSphere Flash Read Cache migrations impose zero impact to the SvMotion
Workflow

21. 22
vSphere Flash Read Cache – XvMotion
In case of manual XvMotion migrations, the flash cache contents options are
the same as vMotion migrations

22. 23
vSphere Flash Read Cache - High Availability (HA)
vFlash Cache vFlash Cache
Restart
vFRC vFRC
Failed
Virtual Flash Cache state is
not persistent across Guest
OS and host lifecycle.
In the event a VM crashes,
since HA will restart the VM
on the same host the cache
will be rebuilt.
For host crashes, the VM
is restarted on a different
host:
 Admission control will
apply.

23. 24
vSphere Flash Read Cache - Distributed Resource Scheduler
XvMotion
vFRC vFRC
Currently virtual flash
resources are managed on
host level only.
No automatic host migration
for resource optimization.
DRS will perform placement
constraints for vMotion and
HA.

24. 25
vSphere Flash Read Cache - Resource Management
• Virtual Flash Resources
• provisioned dynamically across
all the running VMs
• Virtual Machine Failure
• fails to power on if host runs out
of Virtual Flash resource
• Resource Attributes
• Reservations = Limit (no
expandable reservations)
• Shares not supported
• No oversubscription (No thin
provisioning)
• Resource Consumption
• Created only when VM is powered on
• Reclaimed when VM is powered off
• Resized when necessary
• Migrated when VM moves to a different host

25. 26
vSphere Flash Read Cache – Cache Contents is/is Not Preserved
 Across disk close/reopen
 Fast Suspend/Resume (FSR)
 Snapshot
 Clone
 svMotion, XvMotion
 When VM is migrated
(vMotion) using following
option:
 Always migrate vFlash Cache
Preserved
 Suspend
 During vFlash Cache hot
reconfigure
 VM and Host reboot
 Restore Snapshot
 When VM is migrated using
following option:
 Do not migrate vFlash
Cache
Not Preserved

26. 27
Performance & Monitoring

27. 28
vFRC Performance
 What workloads can benefit from vFRC ?
• Read-dominated I/O pattern
• High repeated access of data (E.g. 20% of working set accessed 80% of time)
• Sufficient flash capacity to hold data that is accessed repeatedly

28. 29
vSphere Flash Read Cache Sizing Guidelines
 Define virtual cache working set based on:
• % of VMDK or workload size (for e.g. 20% of database size)
 Once workload is stable, monitor vFRC stats for the following:
• numBlocksCurrentlyCached
• numBlocks
 Define Cache Block Size
• Use vscsiStats to gather workload statistics
• Use the ioLength histogram to identify suitable block size based on the largest
number of I/O operations
rawlinson

29. 30
vSphere Flash Read Cache Monitoring Performance Statistics Counters
A new set of performance statistics counters for Virtual Flash Read
Cache are available in vCenter Server performance manager.

30. 31
vSphere Flash Read Cache – Performance Statistics Counters
v Flas hCac heIops
 Monitors the average number of I/O requests per second to the virtual
disk cache.
 Unit – Number
v Flas hCac heL atenc y
 Monitors the average number of microseconds to complete I/O to the
virtual disk cache.
 Unit – Microsecond
v Flas hCac he T hroug hput
 Monitors the average of caches currently controlled by the module.
 Unit – Number

31. 32
vSphere Flash Read Cache – Cache Statistics in ESXCLI
esxcli storage vflash cache stats get –m <module > - c <cache file>
vFRC Statistics:
esxcli storage vflash cache stats reset
–m <module> -c <cache file>
Virtual Flash Read Cache performance statistics can be retrieved in
greater details utilizing ESXCLI framework

32. 33
Data Warehousing Application
 Benchmark : Swingbench 2.4 using ‘Sales History’ Schema on
Oracle 11g R2 database
 vFRC Configuration: 8GB Cache Size and 8KB Cache block size
Up to 2X improvement in transactions/min, with a 2X reduction in
latency
61.7
112.9
0
20
40
60
80
100
120
Baseline VFRC
TPM
Transac ons Per Minute
20.389
10.859
0
5
10
15
20
25
Baseline VFRC
ResponseTIme(s)
Average Response Time

33. 34
Database Transaction Application
 Benchmark Used : DVDStore
 Simulates online e-commerce site operations
 Database : MS SQL Server 2008
 Database Size : 15 GB
 Workload Characteristics
• 60% reads
• Mostly random I/Os
• Predominant I/O size : 8KB
8802 8937
12319
0
2000
4000
6000
8000
10000
12000
14000
Baseline vFRC - 10GB vFRC - 15GB
Orders Per Minute
Up to 39% improvement in application throughput

34. 35
License & Packaging

35. 36
Licensing

36. 37
Summary

37. 38
Summary
 Simple to use
 Works with any Flash device
type
 Flexible deployment - Flash
not required in every server
 Support for VMFS and NFS
 No agents - Transparent to
the guest OS/App
 Supports VMDK granular
allocation
 Seamlessly work with other
vSphere features
 Significantly improve
application performance
Virtual Flash Resource
vSphere Flash Read Cache
vSphere

38. 39
Other VMware Activities Related to This Session
 HOL:
HOL-SDC-1308
Virtual Storage Solutions
 Group Discussions:
STO1004-GD
vSphere Flash Read Cache, VSAN, VMware Virsto, Software Defined
Storage Architecture with Rawlinson Rivera and Vmware
R&D Engineers

39. THANK YOU

41. vSphere Flash Read Cache Technical Overview
Kiran Madnani, VMware
@kmadnani
Rawlinson Rivera, VMware
@punchingclouds
STO5588
#STO5588