Conclusions

OK, let's summarize:

  • “near” layout is a very reasonable default, as it give very good random I/O and passable sequential speed;
  • “offset” layout is my favorite: it had good random I/O and good sequential speed, showing the better of the two worlds;
  • “far” layout has very high sequential speed, but its lower random I/O performance means that, unless you are sure that your workload is mainly composed of sequential operations, you should avoid it.

Remember that the above tests were done on a 100 GiB disk partition (~200 GiB useful array size). This means that, will full disk partitions, “far” random I/O results can be significantly lower then expected.

Please also note that, while IOMeter is a wonderful tool, it had its limitation. Moreover, no synthetical test can cover 100% of real-world scenarios so it would be preferable to do some quick testing of your specific needs. In my case, as I will use this array to host virtual machine files, I found IOMeter to accurately represent my usage pattern (low metadata overhead, many read/write operations on one or few files, etc.) and so I happily used it ;)

 

I hope that you find this article interesting. If you want, you can discuss it with me using the comment system or by writing at This email address is being protected from spambots. You need JavaScript enabled to view it.

Have a nice day!