V irtual Mattias Sundling Eric Sloof Mythbusting Goes Virtual Mattias Sundling Evangelist Dell Software msundling Eric Sloof VMware Certified Instructor NTPRONL esloof Introduction ID: 446577
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Slide1
Mythbusting Goes Virtual
Mattias Sundling
Eric SloofSlide2
Mythbusting Goes Virtual
Mattias Sundling
Evangelist
Dell Software@msundling
Eric SloofVMware Certified InstructorNTPRO.NL@esloofSlide3
Introduction
VMware vSphere
evolves with every
releaseThings that used to be true aren't true anymore
Engage in virtualization communities and social media to get up to speedSlide4
Agenda/Myths
VMware HA works out-of-the-box
VMware
snapshots impacts performance
Disk provisioning type doesn’t affect performanceAlways use VMware tools to sync the time in your VMSlide5
VMware HA works out-of-the-box
Myth
1Slide6
Most Configured Admission Control Policy
WHY?Slide7
Enabling VMware High AvailabilitySlide8
Host Failures a Cluster Tolerates
ESX01
ESX02
ESX03
Shared storage –
vm.vmdkSlide9
Default minimum Slot size
If you
have not
specified a CPU reservation for a virtual machine, it is assigned a default value of 32MHz.
When the memory reservation is 0, the slot size equals the virtual machine overhead.
32 MHz
69 MB
VM1
VM2
VM3
VM4
VM..nSlide10
Slot size based on reservation
vSphere HA calculates the
CPU and memory slot size
by obtaining the largest CPU and memory reservation of each powered-on virtual machine.
512 MHz
1093 MB
VM1
VM2
VM3
VM4
VM…nSlide11
HA advanced settings
das.slotcpuinmhz
das.vmcpuminmhz
Memory reservation
CPU reservation
SLOT
SLOT
das.slotmeminmb
das.vmmemoryminmbSlide12
Specify a fixed slot size explicitlySlide13
VMs requiring multiple slots
512 MHz
512 MB
VM1
VM2
VM3
VM4
VM5
VM6
Reservation
Slot size
You can also determine the risk of resource fragmentation in your cluster by viewing the number of
virtual machines
that require multiple slots.
VMs might
require multiple slots if you have specified a
fixed slot
size or a maximum slot size using advanced
options.Slide14
Fragmented failover capacity
ESX1
ESX2
ESX3
Shared storage –
vm.vmdkSlide15
Worst case scenario
ESX01 3.6 GHz
16 GB
ESX02 3.6 GHz
16 GB
ESX03 3.6 GHz
32 GB
Shared storage –
vm.vmdkSlide16
Keep hosts the same size
Host memory: 3 * 16 GB
Host memory: 2 * 16 GB
1
* 32 GBSlide17
Percentage of Cluster Resources Reserved
ESX01
ESX02
ESX03
Shared storage –
vm.vmdkSlide18
Percentage reserved as failover capacitySlide19
Admission control based on reservations
vSphere HA uses the actual
individual reservations
of the virtual
machines.
The
CPU component
by summing
the CPU
reservations of
the powered-on
VMs.Slide20
Computing the Current Failover Capacity
If you have not
specified
a CPU reservation for a
VM, it is assigned a default value of 32MHzSlide21
Resources Reserved is not Utilization
The Current CPU Failover Capacity is computed by subtracting the total CPU resource requirements from the total host CPU resources and dividing the result by the total host CPU resources.Slide22
Percentage reserved advanced setting
The default CPU
reservation for a
VM can
be changed using the das.vmcpuminmhz advanced attribute
das.vmmemoryminmb
defines
the default memory resource value assigned to a
VMSlide23
What about the web clientSlide24
Specify Failover Hosts Admission Control Policy
ESX01
ESX02
ESX03
Shared storage –
vm.vmdkSlide25
Specify Failover Hosts Admission Control Policy
Configure
vSphere HA to designate specific hosts as the failover hostsSlide26
The failoverhost
To ensure that spare capacity is available on a failover host, you
are prevented
from powering on
virtual machines or using vMotion to migrate VMs to a failover host.
Also
, DRS does not use a
failover host
for load balancing
If
you use the Specify Failover Hosts admission control policy and designate multiple failover hosts, DRS does not attempt to enforce VM-VM affinity rules for virtual machines that are running on failover hosts.Slide27
Status of the Current Failover Hosts
Red
- The
host is disconnected, in maintenance mode, or has vSphere HA errors.
Green
- The
host is connected, not in maintenance mode, and has no vSphere HA errors.
No powered-on VMs reside
on the host.
Yellow
- The
host is connected, not in maintenance mode, and has no vSphere HA errors. However, powered-on VMs reside on the host.Slide28
Myth busted
VMware High Availability needs to be configured
Be careful with reservations
Always check run-time informationSlide29
VMware snapshots impacts performance
Myth
2Slide30
What is a Snapshot?
Preserves state and data of a VM at a specific point in time
Data includes
virtual disks, settings, memory (optionally)Allows you to revert to a previous
stateTypically used by VM admins when doing changes and by backup softwareESX3, ESX(i)4 had issues with deleting snapshotsESXi5 improved snapshot consolidationSlide31
What is a Snapshot?
File
Description
.
vmdkOriginal virtual diskdelta.vmdkSnapshot delta disk.vmsdDB file
with
relations between snapshots
.
vmsn
Memory file
Snapshot grows in 16MB chunks
Requires locking Slide32
Locks
Locks are necessary when creating
,
deleting and growing snapshot, power on/off, create VMDKESX(i)4 used SCSI-2 reservationLocks entire LUNSlide33
Locks
ESXi5 uses Atomic Test & Set (ATS) VAAI primitive
Locks only individual VM
Requires VAAI enabled array and VMFS-5Slide34
Performance
Locking
ATS increase performance up to 70% compared to SCSI-2 reservation
Normal operations
Snapshot age
Number of snapshots
Snapshot size
Be careful with snapshots in production!Slide35
Improvements to snapshots management and lockingSnapshots still have impact on performance
NOT
Myth NOT BustedSlide36
Disk provisioning type doesn’t affect performance
Myth
3Slide37
Disk typesSlide38
Block allocation
VMDK
Block
Block
Block
VMDK File Size
Written Blocks
Thick Provision Lazy Zeroed
VMDK
Block
Block
Block
VMDK File Size
Written Blocks
Thin
Provision
VMDK
Block
Block
Block
VMDK File Size
Written Blocks
Thick Provision Eager Zeroed
VMDK
VMDKSlide39
The iSCSI Laboratory
Iomega
StorCenter
px6-300d with 6 SATA 7200 DisksWindows 2008 R2
4096 MB – 1 vCPUHardware Version 9VMware vSphere 5.1
Single Intel 1GB Ethernet
Cisco 2960 switch
MTU Size 1500Slide40
3 different disks
Thick Provision Lazy
Zeroed
Thin Provision
Thick
Provision Eager ZeroedSlide41
Thick Provision Lazy Zeroed
Average Write
13.3
MB/s - Access time:
44.8 ms Slide42
Thin Provision
Average Write
13.7
MB/s - Access time:
46.8 ms Slide43
Thick Provision Eager Zeroed
Average Write 86.6 MB/s - Access time: 9.85
ms
Slide44
Comparision
Average Write
13.3
MB/s - Access time: 44.8 ms Average Write
13.7 MB/s - Access time: 46.8 ms Average Write 86.6 MB/s - Access time: 9.85 ms
Thick Provision Lazy Zeroed
Thin Provision
Thick Provision Eager ZeroedSlide45
Migration
Storage
vMotion
is able to migrate the disk format of a Virtual MachineSlide46
Myth busted
Thin and Lazy Zeroed disks have the same speed
Once allocated, these disks are as fast as Zeroed disks
Thick Provision Eager Zeroed offer best performance from first write onSlide47
Always use VMware tools to
sync
the time in your
VM
Myth
4Slide48
Time Sync Problems
VMs have not access to native physical HW timers
Scheduling can cause time to fall behind
CPU / Memory overcommit increases riskPeople are mixing different time sync optionsSlide49
VMware Tools
ESX(
i
) 4 and prior – not possible to adjust time backwardsESXi 5 – Improved time sync to be more accurate and can also adjust time backwards
Enable/Disable periodic sync in VMware Tools GUI, vCenter or VMX fileSlide50
VMware Tools
Default
periodic sync interval is 60 sec
Sync is forced even when periodic sync is disabled:Resume, Revert Snapshot, Disk Shrink and vMotion
In order to disable completely configure vmx fileTesting scenarios
tools.syncTime
= FALSE
time.synchronize.continue
= FALSE
time.synchronize.restore
= FALSE time.synchronize.resume.disk = FALSE time.synchronize.shrink = FALSE
time.synchronize.tools.startup = FALSE time.synchronize.resume.host = FALSE Slide51
Guest OS Services
Windows (W32Time service)
Windows 2000 uses SNTP
Windows 2003+ uses NTP and provides better sync options and accuracyDomain joined VMs sync from DCUse Group Policy to control settings
Linux (NTP)Configure ntpd.confStart ntpd
chkconfig
ntpd
on
/etc/init.d
/ntpd start Slide52
Best Practices
ESX(
i
) hosts:Configure multiple NTP serversStart NTP ServiceVirtual Machines:Disable VMware Tools periodic sync
DC: Configure multiple NTP servers (same as ESX(i) host)Domain joined will sync with DCIf not domain joined then configure W32Time or NTP manuallyDo not use both VMware Tools periodic sync and Guest OS time sync simultaneously!Slide53
Myth Busted
Use W32Time or NTP
Do not use VMware Tools period syncSlide54
Summary
Myth 1: VMware
High Availability needs to be
configured, be careful with reservations and always check run-time information
Myth 2:Improvements to snapshot management and locking but still performance impactMyth 3: Use Thick Eager Zeroed disks for best I/O performanceMyth 4:
Use
W32Time or
NTP to sync
time instead of VMware Tools Slide55
VMworldTV
http://www.youtube.com/VMworldTVSlide56
Questions
Mattias Sundling
Evangelist
Dell Softwaremattias_sundling@dell.com,
@msundlingEric SloofVMware Certified InstructorNTPRO.NL
esloof@ntpro.nl
,
@
esloof