HP xw6400 Mini White Paper page 2

Summary
Depending on such factors as disk technology and application characteristics, RAID 0, a striped array
of disks, can deliver substantial improvement in disk access performance over a single disk
configuration.
Background
Major factors of drive performance are rotational speed, interface type, physical construction of the
drive, and firmware algorithms. Each interface type supports various levels of RAID-enhancing
performance, reliability, or both. The optimum disk drive configuration depends on the intended
usage. Single disk configurations offer good storage capacity and reasonable performance. Single
disk performance is a function of the type of disk, SAS or SATA, and the spindle speed of the disk
drive, 7.2K rpm, 10K rpm, or 15K rpm. Performance and capacity can also be increased by moving
to a RAID configuration. There are three types of RAID configuration supported by the
xw6400/xw8400 workstations. This paper will examine the highest performing configuration – RAID
0 or a striped RAID configuration. A RAID 0 array made up of any of the supported disk drives can
offer higher performance than any of the single disk configurations.
IOMeter
IOMeter was used as the test harness for these benchmarks. It was originally developed by Intel, and
is now maintained by the open source community. Current versions of the test platform can be
obtained from . IOMeter allows the user to create access patterns that vary according
www.iometer.org
to transfer request size, percent random/sequential distribution, and percent read/write distribution.
The following two workloads were used for this paper.
File Server Workload
The File Server workload was created to mimic the disk accesses of a generic file server. The
workload was originally developed by Intel, and is distributed with IOMeter. The workload is defined
to be 80% reads and 20% writes, all from/to random locations on the disk. The size of the data
transfers are predominately 4Kbytes (60%) with some very small 512byte transfers (10%) and some
very large 64K transfers (10%). The remaining 20% of the transfers are as follows: 5% at 1K bytes,
5% at 2K bytes, 2% at 8K bytes, 4% at 16K bytes, and 4% at 32K bytes.
Workstation Workload
The Workstation Workload was created to mimic the disk accesses of a generic workstation. It was
developed by the people at www.StorageReview.com. The workload was specified to model a
workstation usage pattern that involves starting, using, and stopping multiple applications over a
period of time. Initial loading of an application will typically involve sequential accesses as libraries
are loaded. Subsequent accesses will be random as different files are accessed and parts of
applications and data files are swapped to disk. The access pattern is defined to be 80% reads and
20% writes, with 80% of these from/to random disk locations and 20% from sequential locations on
the disk.
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