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Mythbusting Goes V irtual

Mythbusting Goes V irtual. Mattias Sundling Eric Sloof. Mythbusting Goes Virtual. Eric Sloof VMware Certified Instructor NTPRO.NL @ esloof. Mattias Sundling Evangelist Dell Software @ msundling. Agenda/Myths. VMware HA works out-of-the-box VMware s napshots impacts performance

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Mythbusting Goes V irtual

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  1. Mythbusting Goes Virtual Mattias Sundling Eric Sloof

  2. Mythbusting Goes Virtual Eric Sloof VMware Certified InstructorNTPRO.NL @esloof Mattias Sundling EvangelistDell Software @msundling

  3. Agenda/Myths • VMware HA works out-of-the-box • VMware snapshots impacts performance • Disk provisioning type doesn’t affect performance • Always use VMware tools to sync the time in your VM

  4. Myth 1 VMware HA works out-of-the-box

  5. Most Configured Admission Control Policy WHY?

  6. Enabling VMware High Availability

  7. Host Failures a Cluster Tolerates ESX01 ESX02 ESX03 Shared storage – vm.vmdk

  8. 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. VM3 VM4 VM..n VM1 VM2 32 MHz 69 MB

  9. Slot size based on reservation VM1 VM2 VM3 VM4 VM…n • 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

  10. HA advanced settings • das.slotcpuinmhz • das.vmcpuminmhz • das.slotmeminmb • das.vmmemoryminmb Memory reservation SLOT CPU reservation SLOT

  11. Specify a fixed slot size explicitly

  12. VMs requiring multiple slots VM1 VM3 VM2 VM4 VM5 VM6 512 MHz 512 MB Slot size Reservation • 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.

  13. Fragmented failover capacity ESX1 ESX2 ESX3 Shared storage – vm.vmdk

  14. Worst case scenario ESX01 3.6 GHz 16 GB ESX02 3.6 GHz16 GB ESX03 3.6 GHz32 GB Shared storage – vm.vmdk

  15. Keep hosts the same size Host memory: 2 * 16 GB 1 * 32 GB Host memory: 3 * 16 GB

  16. Percentage of Cluster Resources Reserved ESX01 ESX02 ESX03 Shared storage – vm.vmdk

  17. Percentage reserved as failover capacity

  18. 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.

  19. Computing the Current Failover Capacity • If you have not specified a CPU reservation for a VM, it is assigned a default value of 32MHz

  20. 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.

  21. Percentage reserved advanced setting • The default CPU reservation for a VM can be changed using the das.vmcpuminmhzadvanced attribute • das.vmmemoryminmbdefines the default memory resource value assigned to a VM

  22. What about the web client

  23. Specify Failover Hosts Admission Control Policy ESX01 ESX02 ESX03 Shared storage – vm.vmdk

  24. Specify Failover Hosts Admission Control Policy • Configure vSphere HA to designate specific hosts as the failover hosts

  25. 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 balancingIf 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.

  26. Status of the Current Failover Hosts 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. Red - The host is disconnected, in maintenance mode, or has vSphere HA errors.

  27. Myth busted • VMware High Availability needs to be configured • Be careful with reservations • Always check run-time information

  28. Myth 2 VMware snapshots impacts performance

  29. 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 state • Typically used by VM admins when doing changes and by backup software • ESX3, ESX(i)4 had issues with deleting snapshots • ESXi5 improved snapshot consolidation

  30. What is a Snapshot? • Snapshot grows in 16MB chunks • Requires locking

  31. Locks • Locks are necessary when creating, deleting and growing snapshot, power on/off, create VMDK • ESX(i)4 used SCSI-2 reservation • Locks entire LUN

  32. Locks • ESXi5 uses Atomic Test & Set (ATS) VAAI primitive • Locks only individual VM • Requires VAAI enabled array and VMFS-5

  33. 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!

  34. Myth NOT Busted • Improvements to snapshots management and locking • Snapshots still have impact on performance NOT

  35. Myth 3 Disk provisioning type doesn’t affect performance

  36. Disk types

  37. Block allocation Written Blocks Block Block Block Thick Provision Lazy Zeroed VMDK File Size VMDK Written Blocks Block Block Block Thin Provision VMDK File Size VMDK VMDK VMDK Written Blocks Block Block Block Thick Provision Eager Zeroed VMDK File Size VMDK

  38. The iSCSI Laboratory • Iomega StorCenterpx6-300d with 6 SATA 7200 Disks • Windows 2008 R24096 MB – 1 vCPUHardware Version 9 • VMware vSphere 5.1 • Single Intel 1GB Ethernet • Cisco 2960 switchMTU Size 1500

  39. 3 different disks • Thick Provision Lazy Zeroed • Thin Provision • Thick Provision Eager Zeroed

  40. Thick Provision Lazy Zeroed Average Write 13.3 MB/s - Access time: 44.8 ms

  41. Thin Provision Average Write 13.7 MB/s - Access time: 46.8 ms

  42. Thick Provision Eager Zeroed Average Write 86.6 MB/s - Access time: 9.85 ms

  43. Comparision Thick Provision Lazy Zeroed Average Write 13.3 MB/s - Access time: 44.8 ms Thin Provision Average Write 13.7 MB/s - Access time: 46.8 ms Thick Provision Eager Zeroed Average Write 86.6 MB/s - Access time: 9.85 ms

  44. Migration • Storage vMotion is able to migrate the disk format of a Virtual Machine

  45. 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 on

  46. Myth 4 Always use VMware tools to sync the time in your VM

  47. Time Sync Problems • VMs have not access to native physical HW timers • Scheduling can cause time to fall behind • CPU / Memory overcommit increases risk • People are mixing different time sync options

  48. VMware Tools • ESX(i) 4 and prior – not possible to adjust time backwards • ESXi 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 file

  49. 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 file • Testing 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

  50. Guest OS Services • Windows (W32Time service) • Windows 2000 uses SNTP • Windows 2003+ uses NTP and provides better sync options and accuracy • Domain joined VMs sync from DC • Use Group Policy to control settings • Linux (NTP) • Configure ntpd.conf • Start ntpd • chkconfigntpdon • /etc/init.d/ntpd start

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