Date post: | 15-Jan-2015 |
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vSphere Flash Read Cache Technical Overview
Kiran Madnani, VMware
Rawlinson Rivera, VMware
STO5588
#STO5588
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
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
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
6
The Importance of Flash
7
The Importance of Flash Based Devices
Moore’s Law will continue to improve
CPU performance
Disk drive performance remains flat. Time
Perf
orm
ance
FLASH
8
vSphere Platform – Flash
Functions and Considerations
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
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 Pool Flash Pool
New
Accelerate
performance
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
12
vSphere Flash Read Cache
Configuration Options
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Configure Virtual Flash Resource
• vSphere Admin configures Virtual Flash Resource by combining local flash
devices on a single or across multiple hosts
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Configure vSphere Flash Read Cache for VMDKs
• vSphere Admin configures virtual machines to use vSphere Flash Read
Cache for VMDKs.
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
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
17
vSphere Flash Read Cache
and
vSphere Features Interoperability
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
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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
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
21
vSphere Flash Read Cache – SvMotion
vSphere Flash Read Cache migrations impose zero impact to the SvMotion
Workflow
22
vSphere Flash Read Cache – XvMotion
In case of manual XvMotion migrations, the flash cache contents options are
the same as vMotion migrations
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.
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.
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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
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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
27
Performance & Monitoring
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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
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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
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.
31
vSphere Flash Read Cache – Performance Statistics Counters
v F l a s h C a c h e I o p s
Monitors the average number of I/O requests per second to the virtual
disk cache.
Unit – Number
v F l a s h C a c h e L a t e n c y
Monitors the average number of microseconds to complete I/O to the
virtual disk cache.
Unit – Microsecond
v F l a s h C a c h e T h r o u g h p u t
Monitors the average of caches currently controlled by the module.
Unit – Number
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
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 onsPerMinute
20.389
10.859
0
5
10
15
20
25
Baseline VFRC
ResponseTIm
e(s)
AverageResponseTime
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
OrdersPerMinute
Up to 39% improvement in application throughput
35
License & Packaging
36
Licensing
37
Summary
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
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
THANK YOU
vSphere Flash Read Cache Technical Overview
Kiran Madnani, VMware
@kmadnani
Rawlinson Rivera, VMware
@punchingclouds
STO5588
#STO5588