[nycbug-talk] Measuring Disk Performance

Charles Sprickman spork at bway.net
Thu Dec 15 14:55:13 EST 2011

On Dec 15, 2011, at 9:13 AM, Isaac Levy wrote:

> On Dec 12, 2011, at 7:31 PM, Pete Wright wrote:
>> On Mon, Dec 12, 2011 at 11:57:41AM -0500, Isaac Levy wrote:
>>> Hi All,
>>> Disks: I need to measure disk performance across heterogeneous UNIX boxes, and I'm sick of bonnie++ for a bunch of reasons I won't' waste time on here.
>>> I know from conversations that a few folks here have their own ways of testing disks-
>>> I'd really like to know what people do to measure general disk performance?  e.g. really simple tests:
>>> - r/w/d large files
>>> - r/w/d small files
>>> - disk performance when directories contain large numbers of files
>>> I commonly have need to test things like:
>>> - different block sizes
>>> - different inode allocations (UFS/ext3
>>> - different filesystem partition layouts
>>> - different filesystem features (think ZFS fun)
>>> Any thoughts, experiences, urls or shell utils to share?
>> hey ike!
>> there is actually a pretty decent chapter on measuring disk and
>> filesystem performance in "High Performance PostgreSQL 9.0".  
> Is it this book:
> "PostgreSQL 9.0 High Performance"
> Author: Gregory Smith
> Publisher: Packt Publishing

It is.  I just got that, haven't read the whole thing yet, but skimmed it and it is chock-full of good stuff.  I'm just starting to come up with a benchmark methodology for getting hard numbers comparing a spinning disk postgres box vs. and all-SSD postgres box.  That book (and the author, and lots of insanely great people on the postgresql-performance list) has steered me away from some boring and time-wasting benchmarks.

There are also a bunch of tools for postgres that help you test with your own data/workload:


But yeah, even pgbench is going to give your disks a good workout.

I can't emphasize enough just how many hours you can lose if you start browsing the performance mailing list archives.  Fascinating stuff in there.


>> they talk
>> about using a tool, bundled with bonie++, called zcav that will track
>> transfer rates from the begining to end of a disk subsystem.  it also
>> will output data into gnuplot friendly format for pcitures.  i used this
>> quite extensivly while tuning a linux dataware house a while back.
>> other tools that I'm happy with are iozone and fio:
>> http://www.iozone.org/
>> http://freecode.com/projects/fio
>> i find that when doing benchmarking of systems for eval purposes or
>> benchmarking i end up using a mixture of many different tools.  i find
>> that differnent tools will stress different parts of a given i/o
>> subsystem.  so i'd generally do something like:
>> - initial test using dd with variable blocksizes (dependent upon
>> underlying filesystem block size)
>> - several bonie++ tests, followed by some tests using iozone and fio
>> - depending on how system will be used in production i try some
>> application level tests.  for a db - pgbench, webserver apache bench
>> etc..
> Understood, really comprehensive, and valuable!
> Have you posted your methodology and/or resulting tests anywhere?
> --
> Conversely, what I'm looking to really do here, is more of a cave-man sanity test: test a few small common cases in a relative vaccum, ideally using UNIX builtins spitting a few integers back to stdout.  (mix a bit of xargs with rm, mkdir, dd, etc…)
> I'm actually looking to avoid going down this path alltogether, as I'd rather focus this level of detail on measuring disk/system performance as the team hammers our apps.
>> I have also done some interesting testing using
> ..
>> http://tsung.erlang-projects.org/
> *That* looks rad- way off direct disk testing, but that's a very compelling toolkit...
> Thanks Pete!
> Rocket-
> .ike
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Charles Sprickman
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