System information

Choosing Virtual Machine Locations
Storage location is an important factor when you want to optimize the performance of your virtual machines.
There is always a trade-off between expensive storage that offers high performance and high availability and
storage with lower cost and lower performance.
Storage can be divided into different tiers depending on a number of factors:
High tier
Offers high performance and high availability. Might offer built-in snapshots
to facilitate backups and Point-in-Time (PiT) restorations. Supports replication,
full SP redundancy, and fibre drives. Uses high-cost spindles.
Mid tier
Offers mid-range performance, lower availability, some SP redundancy, and
SCSI drives. Might offer snapshots. Uses medium-cost spindles.
Lower tier
Offers low performance, little internal storage redundancy. Uses low end SCSI
drives or SATA (serial low-cost spindles).
Not all applications require the highest performance and most available storage, at least not throughout their
entire life cycle.
If you want some of the functionality of the high tier, such as snapshots, but do not want to pay for it, you
might be able to achieve some of the high-performance characteristics in software.
When you decide where to place a virtual machine, ask yourself these questions:
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How critical is the virtual machine?
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What are its performance and availability requirements?
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What are its point-in-time (PiT) restoration requirements?
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What are its backup requirements?
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What are its replication requirements?
A virtual machine might change tiers throughout its life cycle because of changes in criticality or changes in
technology that push higher-tier features to a lower tier. Criticality is relative and might change for a variety
of reasons, including changes in the organization, operational processes, regulatory requirements, disaster
planning, and so on.
Designing for Server Failure
The RAID architecture of SAN storage inherently protects you from failure at the physical disk level. A dual
fabric, with duplication of all fabric components, protects the SAN from most fabric failures. The final step in
making your whole environment failure resistant is to protect against server failure.
Using VMware HA
With VMware HA, you can organize virtual machines into failover groups. When a host fails, all its virtual
machines are immediately started on different hosts. HA requires SAN storage.
When a virtual machine is restored on a different host, the virtual machine loses its memory state, but its disk
state is exactly as it was when the host failed (crash-consistent failover).
NOTE You must be licensed to use VMware HA.
Fibre Channel SAN Configuration Guide
26 VMware, Inc.