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Installing or upgrading to ESXi 5.1 best practices


This article provides information about upgrading to ESXi 5.1.

  • This article assumes that you have read the vSphere Installation and Setup Guide for ESXi 5.1 Installation or the vSphere Upgrade Guide for ESXi 5.1 upgrades. These guides contains definitive information. If there is a discrepancy between the guide and this article, assume that the guide is correct.
  • VMware provides several ways to install or upgrade to ESXi 5.1 hosts. For more information, see:
    • Methods of installing ESXi 5.1 (2032782)
    • Methods of upgrading to ESXi 5.1 (2032757)


With the introduction of vSphere 5.0, ESX has been discontinued. ESXi is now the only version available for datacenter server virtualization. Due to the architectural changes from ESX to ESXi, not all configuration files, settings, and third party tools are guaranteed to be migrated to ESXi 5.x. Ensure that you retain and note any configuration modifications before performing an upgrade. For more information, see the vSphere Upgrade Guide.

Note: VMware strongly recommends that you make a backup of your virtual machines if they are located on local storage of the ESX/ESXi host before upgrading.

When migrating to ESXi 5.1, ensure that:
  1. Your hardware is compliant on the VMware Compatibility Guide. This includes:
    • System compatibility
    • I/O compatibility (Network and HBA cards)
    • Storage compatibility
    • Backup software compatibility

  2. You have a 64-bit processor. VMware ESXi 5.1 only installs and runs on servers with 64-bit x86 CPUs. It also only supports LAHF and SAHF CPU instructions.
  3. You have an ESXi 5.1 host machine with at least two cores.
  4. The NX/XD bit is enabled for the CPU in the BIOS.
  5. Your processor is supported. ESXi supports a broad range of x64 multicore processors. For a complete list of supported processors, see the VMware Compatibility Guide.
  6. You have 2GB RAM. This is the minimum required to install ESXi 5.1. Provide at least 8GB of RAM to take full advantage of ESXi features and run virtual machines in typical production environments.
  7. Support for hardware virtualization (Intel VT-x or AMD RVI) is enabled on x64 CPUs (to support 64-bit virtual machines). For a complete list of operating systems supported for ESXi, see the VMware Compatibiity Guide. Hosts running virtual machines with 64-bit guest operating systems have these hardware requirements:
    • For AMD Opteron-based systems, the processors must be Opteron Rev E or later.
    • For Intel Xeon-based systems, the processors must include support for Intel Virtualization Technology (VT). Many servers that include CPUs with VT support might have VT disabled by default, so you must enable VT manually. If your CPUs support VT , but you do not see this option in the BIOS, contact your vendor to request a BIOS version that lets you enable VT support.

    Note: To determine whether your server has 64-bit VMware support, download the CPU Identification Utility from vmware.com.

  8. You have one or more Gigabit or 10GB Ethernet controllers. For a list of supported network adapter models, see theVMware Compatibility Guide.
  9. You have controllers with any combination of one or more of:
    • Basic SCSI controllers. Adaptec Ultra-160 or Ultra-320, LSI Logic Fusion-MPT, or most NCR/Symbios SCSI.
    • RAID controllers. Dell PERC (Adaptec RAID or LSI MegaRAID), HP Smart Array RAID, or IBM (Adaptec) ServeRAID controllers.

  10. You have SCSI disk or a local, non-network, RAID LUN with unpartitioned space for the virtual machines.
  11. For Serial ATA (SATA), a disk connected through supported SAS controllers or supported on-board SATA controllers. SATA disks will be considered remote, not local. These disks will not be used as a scratch partition by default because they are seen as remote.

    Note: You cannot connect a SATA CD-ROM device to a virtual machine on an ESXi 5.1 host. To use the SATA CD-ROM device, you must use IDE emulation mode.

  12. You are using a supported storage system. ESXi 5.1 supports installing on and booting from these storage systems: 

    • SATA disk drives. SATA disk drives connected behind supported SAS controllers or supported on-board SATA controllers.

      • LSI1068E (LSISAS3442E)
      • LSI1068 (SAS 5)
      • IBM ServeRAID 8K SAS controller
      • Smart Array P400/256 controller
      • Dell PERC 5.0.1 controller

    • SATA disk drives. Supported on-board SATA include: 

      • Intel ICH9
      • NVIDIA MCP55
      • ServerWorks HT1000

    : ESXi does not support using local, internal SATA drives on the host server to create VMFS datastores that are shared across multiple ESXi hosts.

  13. You have Serial Attached SCSI (SAS) disk drives supported for installing ESXi 5.1 and for storing virtual machines on VMFS partitions.
  14. You have dedicated SAN disk on Fibre Channel or iSCSI
  15. You have USB devices. Supported for installing ESXi 5.1. For a list of supported USB devices, see the VMware Compatibility Guide.
  16. You can install and boot ESXi from an FCoE LUN using VMware software FCoE adapters and network adapters with FCoE offload capabilities. See the vSphere Storage documentation for information about installing and booting ESXi with software FCoE.

ESXi booting requirements

vSphere 5.1 supports booting ESXi hosts from the Unified Extensible Firmware Interface (UEFI). With UEFI you can boot systems from hard drives, CD-ROM drives, or USB media. Network booting or provisioning with VMware Auto Deploy requires the legacy BIOS firmware and is not available with UEFI.

ESXi can boot from a disk larger than 2TB provided that the system firmware and the firmware on any add-in card that you are using support it. See the vendor documentation.

Note: Changing the boot type from legacy BIOS to UEFI after you install ESXi 5.0 may cause the host to fail to boot. In this case, the host displays an error message similar to:

Not a VMware boot bank. Changing the host boot type between legacy BIOS and UEFI is not supported after you install ESXi 5.1.

Storage requirements

ESXi 5.1 has these storage requirements:

  • Installing ESXi 5.1 requires a boot device that is a minimum of 1GB in size. When booting from a local disk or SAN/iSCSI LUN, a 5.2GB disk is required to allow for the creation of the VMFS volume and a 4GB scratch partition on the boot device. If a smaller disk or LUN is used, the installer attempts to allocate a scratch region on a separate local disk. If a local disk cannot be found, the scratch partition (/scratch) is located on the ESXi host ramdisk, linked to /tmp/scratch. You can reconfigure /scratch to use a separate disk or LUN. For best performance and memory optimization, VMware recommeds that you do not leave /scratch on the ESXi host ramdisk. 

  • To reconfigure /scratch, see Set the Scratch Partition from the vSphere Client in the vSphere Installation and Setup documentation

  • Due to the I/O sensitivity of USB and SD devices, the installer does not create a scratch partition on these devices. As such, there is no tangible benefit to using large USB/SD devices as ESXi uses only the first 1GB. When installing on USB or SD devices, the installer attempts to allocate a scratch region on an available local disk or datastore. If no local disk or datastore is found, /scratch is placed on the ramdisk. You should reconfigure /scratch to use a persistent datastore following the installation. 

  • In Auto Deploy installations, the installer attempts to allocate a scratch region on an available local disk or datastore. If no local disk or datastore is found /scratch is placed on ramdisk. You should reconfigure /scratch to use a persistent datastore following the installation. 

  • For environments that boot from a SAN or use Auto Deploy, it is not necessary to allocate a separate LUN for each ESXi host. You can co-locate the scratch regions for many ESXi hosts onto a single LUN. The number of hosts assigned to any single LUN should be weighed against the LUN size and the I/O behavior of the virtual machines.
Based on VMware KB 2032756

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