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How would I find out how many IOPS my Linux system can handle?

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2 Answers 2

up vote 10 down vote accepted

I'm a big fan of iozone myself

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It's worthy to note that iozone has an option to use O_DIRECT, which bypasses the file-caching utility to get a better sense of how the storage actually behaves. –  sysadmin1138 Feb 12 '11 at 15:56
    
Can you give a command line example of using iozone for my purposes on /dev/sdb1? –  Henno Feb 12 '11 at 16:00
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@Henno First, format the drive with the filesystem of your choice. `cd \testfs ; iozone -s 4g -r 2k -r 4k -r 8k -r 16k -r 32k -O -b \tmp\results.xls`` Will test with a 4GB file with I/O sizes of 2-32KB. It will perform all the IOZONE tests, report in I/O Ops, and write an Excel file with the results. –  sysadmin1138 Feb 12 '11 at 16:06
    
@sysadmin1138 How long should that run? It's been running for 15 hours already. Is that normal? –  Henno Feb 13 '11 at 8:00
    
@henno It can run for up to a couple hours. –  sysadmin1138 Feb 13 '11 at 16:08
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Generally you will want to use a benchmark utility like fio. When measuring the amount of IOPs keep in mind that you need to think about things such as:

  • Block size
  • If these are writes, reads, or a mixture
  • If the activity is sequential or random
  • The number of outstanding requests

These will all effect the amount of IOPs you get. You want to make sure that with these tests you consider the response time it takes to fulfill these requests in the results.

Also remember when performing these tests you want to make sure that you flush the file cache (Howto here: deleting linux cached ram) before each test and that your test file is larger than any controller/disk caches.

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I'm just about to create an ext4 partition for the vm I'm going to be testing the I/O on. Mkfs.ext4 allows for many options. Is there anything special I should specify if I only care about performance and not about slack? Like block size? –  Henno Feb 12 '11 at 15:56
    
@Henno: That will probably be best to ask as a new question: "What ext4 options should I consider tuning for performance when making a new filesystem?" or something like that ... –  Kyle Brandt Feb 12 '11 at 16:13
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