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Validating Your Disk Performance

DZone's Guide to

Validating Your Disk Performance

· Performance Zone
Free Resource

Evolve your approach to Application Performance Monitoring by adopting five best practices that are outlined and explored in this e-book, brought to you in partnership with BMC.

Databases and data stores in general (yes, including the leading the leading NoSQL products such as MongoDB and Cassandra) love IO. The more RAM and SSD they have, the better performance you will get...

If you are short of RAM and get a poor performance, it may be a good time to verify your disks performance and see if they do match your needs.

How much IO do you need?

To analyze your needs you should use iostat. This utility will show for each mounted disk the actual number of blocks that are read from disk and are written to disk.

If the numbers are constantly higher than 1,000 blocks/sec, you should consider improving your application design or move from magnetic disks to SSD. In the case below for example the system has a write issue.

> iostat 2
Linux 2.6.32-358.11.1.el6.x86_64 (example.com)         07/26/2014      _x86_64_        (16 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2.02    0.00    0.92    0.01    0.00   97.04

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda              92.88       599.18      3920.00  547971262 3584968522
sdb               0.00         0.00         0.00       3104          0

What are Your Disks Limits?

If you are not sure how much can you get from your disks, Bonnie++ is a great tool to explore your current limits.

Installing Bonnie++

> wget http://www.coker.com.au/bonnie++/bonnie++-1.03e.tgz
> tar xvfz bonnie++-1.03e.tgz
> cd bonnie++-1.03e
> make
> make install

Running Bonnie++

Select your target disk, the size of written data in MB (the -s flag), the number of repeats (the -n flag) and the server RAM size in MB (the -r flag). Please notice that you should define a write to disk value that is larger than the actual RAM value in order to avoid false results:

 > sudo ./bonnie++ -u root -d /tmp -s 1500 -n 3 -r 750

Detecting an issues

As you will be able to see in the following lines Bonnie++ is very useful in detecting disk performance issue and failed disks (see Server C that has a very poor write performance)

Server A (SAS Disks) Results

Version 1.03e       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
serverA        100M 52626  99 +++++ +++ +++++ +++ 61374  99 +++++ +++ +++++ +++
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP

Server B (SSD Disks) Results

Version 1.03e       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
serverB        100M 61864  99 +++++ +++ +++++ +++ 58338  99 +++++ +++ +++++ +++
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                  3 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++

Server C (Failed SSD Disks) Results

Version 1.03e       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
serverC        100M  3892  99 104779  99 98847  99  3865  99 +++++ +++ +++++ +++
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                  3 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
responder5.spd.co.il,100M,3892,99,104779,99,98847,99,3865,99,+++++,+++,+++++,+++,3,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

Bottom Line

When you plan your next move, you should verify your servers can handle it. These tools will help you verify at least your disk can take care of the your future tasks.

Keep Performing,

Moshe Kaplan

Learn tips and best practices for optimizing your capacity management strategy with the Market Guide for Capacity Management, brought to you in partnership with BMC.

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Published at DZone with permission of Moshe Kaplan, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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