vSAN Storage Policy Design for the Management Domain
After you enable and configure VMware vSAN in VMware Cloud Foundation, you can create
storage policies that define the virtual machine storage characteristics. Storage
characteristics specify different levels of service for different virtual machines.
Configure policies according to the business
requirements of the application. By using policies, vSAN can adjust the performance and the
availability of a disk on the fly.
Policy design starts with assessment of business needs and application requirements. Assess the use cases for VMware vSAN to determine the necessary policies. Start by assessing the following application requirements:
- I/O performance and profile of your workloads on a per-virtual-disk basis
- Working sets of your workloads
- Hot-add of additional cache (requires repopulation of cache)
- Specific application best practice (such as block size)
After assessment, configure the software-defined storage module policies for availability and performance in a conservative manner so that consumed space and recoverability are balanced. Usually the default system policy covers most common cases. You create custom policies if specific requirements for performance or availability exist.
If you do not specify a user-configured policy, vSAN uses a default system policy of 1 failure to tolerate and 1 disk stripe for virtual machine namespace and virtual disks. To ensure protection for critical virtual machine components, vSAN uses the policy set on virtual machine namespace for swap files. vSAN also uses the policy set on the virtual disk for the associated snapshot delta disks, if exist.
Object Type | Policy | Comments |
|---|---|---|
Virtual machine namespace | User-configured storage policy | Can be any storage policy configured on the system. |
Swap | Uses the virtual machine namespace
policy | Same as the virtual machine namespace
policy. |
Virtual disks | User-configured storage Policy | Can be any storage policy configured on the system. |
Virtual disk snapshots | Uses the virtual disk policy | Same as the virtual disk policy. |
Decision
ID | Design
Decision | Design
Justification | Design
Implication |
|---|---|---|---|
VCF-MGMT-VSAN-CFG-013 | Use the default
VMware vSAN storage policy. | Provides the level
of redundancy that is needed in the management cluster. Provides the level
of performance that is enough for the individual management
components. | You might need
additional policies for third-party virtual machines hosted in
these clusters because their performance or availability
requirements might differ from what the default VMware vSAN
policy supports. |
VCF-MGMT-VSAN-CFG-014 | Leave the default virtual machine swap file as a sparse object
on VMware vSAN. | Sparse virtual swap files only consume capacity on vSAN as they
are accessed. As a result, you can reduce the consumption on the
vSAN datastore if virtual machines do not experience memory
over-commitment which requires the use of the virtual swap
file. | None. |
Decision
ID | Design
Decision | Design
Justification | Design
Implication |
|---|---|---|---|
VCF-MGMT-VSAN-CFG-015 | Add the following
setting to the default vSAN storage policy: Secondary Failures
to Tolerate = 1 | Provides the
necessary protection for virtual machines in each availability
zone, with the ability to recover from an availability zone
outage. | You might need
additional policies if third-party virtual machines are to be
hosted in these clusters because their performance or
availability requirements might differ from what the default
VMware vSAN policy supports. |
VCF-MGMT-VSAN-CFG-016 | Configure two fault
domains, one for each availability zone. Assign each host to
their respective availability zone fault domain. | Fault domains are
mapped to availability zones to provide logical host separation
and ensure a copy of vSAN data is always available even when an
availability zone goes offline. | Additional raw
storage is required when the secondary failure to tolerate
option and fault domains are enabled. |