Areca RAID 5 performance

[cjlindem]

I upgraded my home server over the last week and am running an Arcea ARC-1222 8-port PCIe-x8 SATA RAID controller card. The server had previously used 2x Western Digital 320GB RE (raid edition 1) drives in software Raid 1. I bought 3x newer model Western Digital 320GB RE3 drives so that combined with the older drives, I could have 4 320GB drives in a RAID5 array plus a hotspare.

To start I installed the 3 new RE3 drives into an array. HDtune benchmarked it at around 200MB/sec which I was very happy with. The first night the 1st disk in the array failed and the controller's alarm went off. I unplugged and replugged the drive, it picked back up, the array rebuilt. Later in the day I rebooted, and the disk dropped from the array again. Fed up, I replaced it with one of the RE1 drives. After the rebuild HDtune only gets around 115MB/s.

I emailed Areca's support to ask what might cause such a big performance drop, and they replied that 115MB/s is what they would expect on a 3-disk raid5, and that they thought 200MB/s was unusual. They said that array performance "depends on the drive throughput". Not all that helpful. I looked up the Raid Edition1 drives and see that they are the original Sata spec. Sata 150. And the newer batch of drives are Sata 300. Either way, none of the drives should be able to saturate even the 150 interface.

Now this is completely speculation, but the best hypothesis I can come up with is that the RE1 drive is a bit slower than the RE3 drives. And the RE3 drives are being 'underclocked' by the controller card to better match the RE1. And then this is all working together to cause the ~80MB/sec performance drop I'm seeing.... does this make any sense??

Thanks for any help,

 

[Blue Fox]

It's all drive limited. The 1222 is capable of about 800mb/s.

 

[cjlindem]

I know the controller card is definitely capable of more (like I said it was getting 200MB/s not long ago). The question really, is why putting a -slightly- slower drive into the array caused 40% performance drop on the array

 

[Blue Fox]

The older drives are probably 40% slower than the newer ones. The array is only as fast as the slowest drive.

 

[cjlindem]

Well I just tested both the Raid Edition 3, and the Raid Edition 1 as stand alone drives. Going into it, I was so sure they would have similar performance. And Blue Fox, you hit it right on the head... the RE1 drive is almost exactly 40% slower than the RE3. Did hard disk technology really advance so much in a few years?

WD3202ABYS (RE3) results:
Transfer rate: MB/s
Minimum: 51.2
Maximum: 109.1
Average 87.1

WD3200SD (RE1) results:
Transfer rate: MB/s
Minimum: 33.2
Maximum: 61.7
Average: 51.6

 

[Blue Fox]

Newer drives are actually considerably faster than even the RE3 you have.

 

[Dangman]

Did hard disk technology really advance so much in a few years?

Yes. A little bit of evidence:

2006: Seagate 7200.9 160GB HDD:

2007: Seagate 7200.10 320GB HDD:

2008: Seagate 7200.11 1TB HDD:

2008: Western Digital WD6400AAKS:

2010: Western Digital WD5000AAKS (Single platter version)


So yeah in a span of 4 years, max transfer speeds has jumped up near 50%. Minimum transfer speeds jumped up near 95%. So HDD tech has advanced quite a bit in the last few years.