RAID 5 NAS Performance
11. RAID 5 NAS Performance
Updated 8/1/2006
So, how good is the DIY RAID 5 NAS? Figures 24 through 27 compare the performance of the DIY RAID 5 NAS to Buffalo Technology's 1 TB TeraStation NAS. The same iozone procedure was used to take all of the data shown, but I ran iozone on a Windows XP Pro, 2.4 GHz Celeron P4, 1 GB RAM machine. So while the results aren't exactly apples-to-apples, the test machines used are close enough in configuration to allow a reasonably accurate comparison.
Figure 24: Write Performance w/ 100 Mbps LAN
Figure 25: Read Performance w/ 100 Mbps LAN
Figure 26: Write Performance w/ 1000 Mbps LAN
From the benchmark results, it is clear that if you are going to build your own NAS, you want to build it with a gigabit Ethernet card. On smaller file sizes, the gigabit-equipped DIY RAID 5 NAS is clearly superior on both writes and reads. But on very large files, it is slower than the TeraStation.
Figure 27: Read Performance w/ 1000 Mbps LAN
This behavior holds up regardless of operating system used on the DIY NAS. Just for fun, I installed Free NAS .671 to compare with the Ubuntu results. Averages tend to hide things, but I've computed the average read and write speeds for the TeraStation and the DIY RAID 5 NAS using Ubuntu and FreeNAS .671 and summarized the results in Table 2. The read and write results represent the average of 32, 64, 128, 256, 512 and 1024 MB file size runs using 64 kB record size.
The averaged results show that the DIY server using Ubuntu comes out a little faster with a 100 Mbps connection, but blows away the Terastation with a gigabit Ethernet connection - even without using Jumbo frames! Since a gigabit Ethernet NIC costs less than $20, its inclusion in any DIY NAS is a no-brainer.
| Test
Configuration |
TeraStation NAS 1.0 TB | DIY RAID 5 NAS | |
|---|---|---|---|
| Ubuntu 6.06 DT | FreeNAS .671 | ||
| Avg Write
1000 Mbps |
7,036 | 23,940 | 4,479 |
| Avg Read
1000 Mbps |
11,900 | 27,566 | 20,152 |
| Avg Write
100Mbps |
4,897 | 5,059 | Not Tested |
| Avg Read
100Mbps |
8,299 | 9,136 | Not Tested |
Table 2: Average Performance Summary- DIY NAS vs. Buffalo Terastation
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An excellent article. I have been trying to setup something like this. I just went thru 2 weeks of trying to get software raid 5 to work in Ubuntu. I searched the net for how-to or step by step instructions and could only find bits and pieces. Nothing worked. Linux users need to remember that us wanna bees don't know even the slightest of commands! In every article I found, they assumed you knew "some" basic commands. I tried reading and learning, but I couldn't find a good learner for linux. Anyway, having decided to do a hardware raid 5 with Ubuntu desktop seemed like my only hope. Then I find this article here, and it is exactly the way EVERY article should be done, step by step, assuming the reader knows nothing. This article is VERY good and thorough! Congratulations Benjamin Webb, you did a great job! -Blueuniform
interesting article, but the beauty of linux software RAID5 is that an array rebuild will happen automatically when you replace the faulty drive (well you have to tell it that you replaced the drive using mdadm). you can even simulate a failure and then watch it rebuild the array to get an idea of how your system will respond under different scenarios. here's a snippet of what needs to be done to replace the missing drive/partition:
Rebuilding:
To remove the failed partition and add the new parition:
mdadm /dev/mdX -r /dev/sdYZ -a /dev/sdYZ
where X is the array number (0,1,etc) and YZ is your disk/partition (sda3 for example)
e.g.:
mdadm /dev/md0 -r /dev/sde3 -a /dev/sdr3
(where sde3 is the 3rd partition on your faulty drive, and sdr3 is the 3rd partition on the new drive)
Watch the automatic reconstruction run with:
watch -n1 cat /proc/mdstat
I understand that people fear the console commands. It can be a bit scary at first. But mdadm is pretty simple when you're used to console apps and a little bit of linux. It's mostly just mdadm and such. I currently run two software raids with 7 and 5 disks.