Dell PowerVault MD3000 - Manual (Page 5)

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices
December 2008 – Revision A01 Page 5
The answers include:
• “It depends…” There are no absolute answers. Each environment is
unique and the correct settings depend on the unique goals,
configuration, and demands for the specific environment.
• “Actual mileage may vary.” Results vary widely because conditions
vary widely.
The answers to this question suggest the following basic approach to
performance tuning:
1 – Configure and test
2
– Measure
3 – Adjust as required
The performance monitoring features in all MD3000 and MD3000i storage
systems and the controls for tuning make them ideally suited for this iterative
process. The first step in tuning is to establish a baseline of existing
performance. When generating a performance baseline, it is ideal to use a
workload that is as similar to the intended final use of the storage solution. This
can be as simple as the real application or a SQL Replay with a system
performance monitor (perfmon or sysstat/iostat as well as the CLI and state-
capture performance monitoring) or a synthetic benchmark package that closely
imitates the expected I/O profile (Iometer, IOZone, Bonnie). By comparing the
baseline data to the estimated needs and capability of the configuration, the user
can effectively tune an MD3000 or MD3000i storage array. This white paper
provides recommendations for this important first step as well as tuning tweaks to
get the full capabilities from the MD3000 and MD3000i storage systems.
3 Application Software Considerations
In understanding the I/O characteristics of intended applications using the
storage in a manner as close to the expected run-time is required to determine
the optimal storage and system configuration, and is critical to tuning the overall
solution. This includes, but is not limited to the following:
• Number of discrete I/O sources interacting with the solution
• Randomness of data access by the primary I/O source(s)
• Mean size of typical I/O; this is usually divided into the following three
categories:
o
Large Block ( ≥256KiB ) transfer size
o
Medium Block (≥32KiB and < 256KiB) transfer sizes
o
Small Block ( < 32KiB) transfer sizes
• Burstiness of I/O pattern, i.e. the mean duty-cycle of I/O to the storage
array