IntelliCache 编辑

Note:

This feature is only supported when using Citrix Hypervisor with Citrix Virtual Desktops.

Intellicache is not supported for VMs using a GFS2 SR.

Using Citrix Hypervisor with IntelliCache makes hosted Virtual Desktop Infrastructure deployments more cost-effective by enabling you to use a combination of shared storage and local storage. It is of particular benefit when many Virtual Machines (VMs) all share a common OS image. The load on the storage array is reduced and performance is enhanced. In addition, network traffic to and from shared storage is reduced as the local storage caches the primary image from shared storage.

IntelliCache works by caching data from a VMs parent VDI in local storage on the VM host. This local cache is then populated as data is read from the parent VDI. When many VMs share a common parent VDI, a VM can use the data read into the cache from another VM. Further access to the primary image on shared storage is not required.

A thin provisioned, local SR is required for IntelliCache. Thin provisioning is a way of optimizing the use of available storage. This approach allows you to make more use of local storage instead of shared storage. It relies on on-demand allocation of blocks of data. In other approaches, all blocks are allocated up front.

Important:

Thin Provisioning changes the default local storage type of the host from LVM to EXT4. Thin Provisioning must be enabled in order for Citrix Virtual Desktops local caching to work properly.

Thin Provisioning allows the administrator to present more storage space to the VMs connecting to the Storage Repository (SR) than is available on the SR. There are no space guarantees, and allocation of a LUN does not claim any data blocks until the VM writes data.

Warning:

Thin provisioned SRs may run out of physical space, as the VMs within can grow to consume disk capacity on demand. IntelliCache VMs handle this condition by automatically falling back to shared storage when the local SR cache is full. Do not mix traditional virtual machines and IntelliCache VMs on the same SR, as IntelliCache VMs can grow quickly in size.

IntelliCache deployment

IntelliCache must be enabled either during host installation or be enabled manually on a running host using the CLI.

We recommend that you use a high performance local storage device to ensure the fastest possible data transfer. For example, use a Solid State Disk or a high performance RAID array. Consider both data throughput and storage capacity when sizing local disks. The shared storage type, used to host the source Virtual Disk Image (VDI), must be NFS or EXT3/EXT4 based.

Enable on host installation

To enable IntelliCache during host installation, on the Virtual Machine Storage screen, select Enable thin provisioning. This option selects the host’s local SR to be the one to be used for the local caching of VM VDIs.

Convert an existing host to use thin provisioning

To delete an existing LVM local SR, and replace it with a thin provisioned EXT3/EXT4 SR, enter the following commands.

Warning:

These commands remove your existing local SR, and VMs on the SR are permanently deleted.

    localsr=`xe sr-list type=lvm host=hostname params=uuid --minimal`
    echo localsr=$localsr
    pbd=`xe pbd-list sr-uuid=$localsr params=uuid --minimal`
    echo pbd=$pbd
    xe pbd-unplug uuid=$pbd
    xe pbd-destroy uuid=$pbd
    xe sr-forget uuid=$localsr
    sed -i "s/'lvm'/'ext'/" /etc/firstboot.d/data/default-storage.conf
    rm -f /var/lib/misc/ran-storage-init
    systemctl restart storage-init.service
    xe sr-list type=ext
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