Veritas Storage Foundation Intelligent Storage Provisioning 5.0 Solutions Guide, HP-UX 11i v3, First Edition, May 2008

21Tiered storage solutions
Policies for storage tiers
The following table shows the typical factors that can be taken into account
when implementing policies for storage tiers.
An ideal policy ensures that files are placed on the most appropriate type of
storage when they are created, and that they are relocated to different tiers of
storage during their life cycle. File relocation may be triggered according to
various criteria such as frequency of access, ownership and size changes.
To set up a storage tier begin by tagging those volumes that you want to place in
a tiered hierarchy, add these volumes to a volume set, and then implement the
policies your enterprise has decided to use. For example, a policy might say that
customer transaction records should be moved from the top tier (for example,
gold) to a middle tier (silver) when they have not been accessed for 30 days, and
from the middle tier to the lowest tier when they have not been accessed for 120
Factor Description
Availability Some files are more valuable than others to an
enterprise. For example, losing a day's business
transactions is significant but probably
survivable. Losing quarterly or annual closing
figures, on the other hand, might be
catastrophic. Losing an entire day's work is a
significant setback for an employee, but losing
the finished product is a much more serious
setback for the company.
Business considerations Enterprise accounting, security, and regulatory
compliance may require that specific files or
types of files be confined to certain storage
devices.
Expected access patterns Different types of data need different levels of
I/O performance. Streamed data requires high
bandwidth for data transfer performance, but
moderate I/O request rates are often
acceptable. Transactional data requires high
I/O request rates, but the bandwidth
requirements may not be critical if only small
amounts of data are involved.
Load balancing Applications that run concurrently may
compete for I/O resources unless their data is
placed on separate storage devices with
separate access paths.