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Getting started with Flash Accel : Enabling VMs and disks for caching

Enabling VMs and disks for caching
You can allocate cache to a VM and enable the VM and its disks for caching in the same step. You can also enable cache metrics collection for the VM and its disks. Of course, you can perform each of these tasks individually if you prefer.
Before you begin 
The virtual machine must be configured with memory sized appropriately for the cache size, approximately 0.6 GB of RAM for every 100 GB of cache. So if you are planning to provide 250 GB of cache for the virtual machine, you should configure 1.5 GB of RAM (in addition to whatever RAM is required to run the virtual machine and applications).
Flash Accel uses a physical Raw Device Mappings (pRDM) device to represent the cache to the virtual machine. The RDMP file for the device cannot be stored in an NFS datastore. If the files for the VM are stored in an NFS datastore, its host must have access to a VMFS datastore for the RDMP file.
About this task 
If you have enabled vMotion migration, the amount of cache space you can allocate to the VM is limited not only by the cache space available on its host, but also by the cache space available on its potential migration targets. In other words, if the VM resides on host X, with 100 GB of unallocated cache, and host Y and host Z are both potential migration targets, with 75 GB and 50 GB of unallocated cache, respectively, the maximum cache space you can allocate to the VM is 50 GB.
Note: If the VM host and migration targets are members of a cluster with VMware DRS/HA enabled, you should add VM-Host affinity rules to the DRS cluster configuration. Adding affinity rules ensures that the VM is provisioned only on Flash Accel-enabled hosts.
Steps 
1.
The Cache Space dialog box opens.
2.
To enter the cache size manually, click the Enter Manually check box, then enter the cache size in the Enter Cache Space Size field.
Leave the check boxes for Enable caching for the VM and its disks and Enable cache metrics collection for the VM and its disks selected.
3.
Click Allocate.
Result 
The Cache Size field for the VM is set to the specified value. The Cache State field for the VM is set to Enabled.
After you finish 
After cache space allocation completes, make sure to disable caching for the boot disk and any other disks that should not be cached.
Wait until the cache is populated with data from typical application read and write activity, or fully warmed, before you begin tracking performance statistics. The amount of time until full cache warming varies depending on the working set size of the application data and the I/O access rate.
Parent Topic: Getting started with Flash Accel
Previous Topic: Preparing for vMotion migration


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