Re: measuring RAID arrays performances
On 5/25/2013 5:36 PM, Jean-Marc wrote:
> Hi guys,
>
> I am trying to measure the perf' of RAID arrays to be sure of the layout
> I'll use for my future set up.
>
> Based on this article, RAID10,f2 seems to be the best set up:
> https://raid.wiki.kernel.org/index.php/Performance
>
> But if I create a RAID10,f2 array (ext4 FS) and if I compare its perf'
> against a RAID1 arrays using bonnie++, I do not see any big differences.
...
> May be I am doing something wrong.
Yes, you are. You're using only 2 disk drives. The md/RAID10 module
with two drives will perform nearly identical to RAID1.
Adding insult to injury you are using 6GB partitions in your testing
setup. The "layouts" of md/RAID10 are only of benefit when you use the
entire disk capacity, or a very large portion of it. These layouts
obtain some advantage be changing the behavior of the disk head and thus
read latency. With a 6GB partition on a 1/2TB disk drive, the heads
will never travel outside of a single track.
You really need to read and comprehend much more about md, or simply
listen to an expert:
For two disks, use RAID1. PERIOD. End of story. Screwing with
anything else is a massive waste of your time. If you have 3 or more
disks, then you can worry about layouts.
--
Stan
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