Scale Computing HC3s HyperCore Enhanced Automated Tiering (HEAT) is an extension of the SCRIBE storage layer that is available to HC3 hybrid clusters with 3 nodes or more.
HEAT allows virtual disk level, priority data placement for allocated data (actual consumed capacity on a VM virtual disk). This is accomplished through a real-time heat map of virtual disk I/O in order to “tier” the data. Data blocks that are “hot” (=accessed regularly by the virtual disk) are stored at the SSD level while “colder” data blocks are stored at the HDD level.
There are 4 basic HEAT principles:
1. All VMs have access to SSDs, no matter what node the VM may actually be running on.
2. SSDs are additional capacity for VM disks (subvirtual tiering), not a cache for system data.
3. Administrators have granular control of SSD access at the VM virtual disk level.
4. Administrators are able to mix and match Tiered HC3 nodes with standard HC3 nodes and Storage Only nodes without any extra work or requirements.
The HC3 web interface provides an easy-to-use slide bar on the property page of an individual virtual disk in order to set the flash priority level of a VM’s virtual disk data:
2 Very Low
4 Normal (default)
6 Very High
10 Ludicrous Speed
11 These go to 11
When the flash priority level is set to 0, no data on the virtual disk ever gets promoted to the SSD layer. When the flash priority level is set to 11, all data on the virtual disk is promoted to the SSD layer.
Altering HEAT priority will effect all VM virtual disks within the HC3 cluster. Each increase in flash priority access will dedicate roughly twice as much flash capacity for the VM virtual disk, and consequently reduce the flash capacity available for other VM virtual disks on the system.