Dell PowerVault 221S (SCSI) - Manual (Page 4)

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02
PAGE 4 11/17/2005
Understanding each of the storage components with respect to these attributes will help in
making intelligent decisions to determine an optimal configuration for a given application.
The paper presumes that the reader has a basic understanding of different levels of RAID
and interconnects technologies – Parallel SCSI (SPI-4), PCI vs. PCI-X vs. PCI-e. This
paper presents a study of all storage components, as identified earlier, against various
storage applications and different operating environments; however, specific behavior of
each of the storage applications and management functions is beyond the scope of this
document. In this document we present storage solution from Parallel SCSI perspective,
specifically for Dell’s Direct Attached Storage (DAS) products. Other storage technologies
such as SAS, SATA, or Fibre Channel, as well as topologies such as Network Attached
Storage (NAS) or Storage Area Network (SAN) are outside the scope of this document. All
storage applications referred to herein are treated independent of any specific host system
or server.
2. Storage Applications and Components
Identify customer usage model and needs
In order to select the correct storage solution for any given situation, it is important to
understand what the application and user requirements will be for that solution. A good
starting point is to have an understanding of basic storage profiling considerations.
• Table 2-1: Storage Profiling Considerations
Characteristic Values Description
Performance
• Bandwidth (MB per
sec.)
• I/O size (KB/MB)
• I/O Profile (read/write
and random/sequential
access mix)
• Latency
Performance is the overall ability of the solution to read
and write data to disk. The performance requirements
are usually determined by the type of application being
utilized. Different applications have different
performance requirements. For example, a database
or e-mail server has mostly random disk access
operations while a streaming media server would have
mostly sequential disk access.
Storage Capacity
Needs
Gigabytes
Storage capacity is the current amount of storage
space required by the application and user data. For
example, e-mail storage for 100 users would require
much less storage capacity than an e-mail store for
1000 users.
Storage Growth
Rate
Percent increase per
year
Storage growth is the expected increase in the amount
of capacity that will be required as usage of the server
increases. This is usually measured in the expected
number of users or clients accessing the server
Criticality
Low, Medium, High,
Very High
Criticality defines the impact to mission critical business
needs if the storage is offline. This characteristic is
important for choosing the right RAID level, and
determining if clustering is needed.
Picking a solution based on the application profile
One of the most important factors to consider when selecting a storage solution is the type
of application that will be utilizing the storage solution. This defines the overall purpose of