I personally use all WD Greens because they spin a bit slower and use less power. Not that I'm a saving the planet kind of guy, but it allows me to keep my case cooler and I can use a smaller power supply.

EDIT: But now after reading this: "For this reason, if possible, use a disk with a higher rotational speed for the parity disk, as it is involved in every "write" to the array.

It won't hurt, but it probably won't help much either unless you are writing simultaneously to a 7200 RPM data drive, or to more than one 5400 RPM data disk at the same time. 

So can we deduce that if we have at least 1 5400 rpm 2TB data drive then a 2TB parity drive that's 7200 rpm would be pointless? I was going to spend an extra £20 for a 7200 on my parity drive but after reading Rajahal explanation I don't think I'll need to now.  

 

This is not true.

 

If you are writing to an array disk that is a 7200 RPM disk, and your parity disk is 7200 RPM, you will have improved write performance, even if every other data disk in your array is 5400 RPM.

 

But if your parity is 5400 RPM, it wouldn't matter if every data disk was 7200 RPM, you'd still get the slightly slower write performance.

 

As others have said, the slight write performance boost is often not worth the extra cost, extra power consumption, and extra heat generated by the faster spinning disks.  But this is a personal decision for each user.  I personally have a 7200 RPM parity, and a few 7200 RPM data disks for my most frequently updated data.  The rest are 5400 RPM.

Thanks, that settles it, I'm definitely getting the 7200 rpm for parity as I have 3x 1TBs that are 7200 also (along with 1.5 & 2TB's that are 5400).

 

Also it's strange that 7200 SATA 6Gb/s drives are cheaper than 3Gb/s ones these days! I know there's negligable increase in speed though.

Only 50p extra for a 2port SATA 6Gb/s PCI-E 1x card over the 3Gb/s version from Scan.

Thanks, that settles it, I'm definitely getting the 7200 rpm for parity as I have 3x 1TBs that are 7200 also (along with 1.5 & 2TB's that are 5400).

 

Also it's strange that 7200 SATA 6Gb/s drives are cheaper than 3Gb/s ones these days! I know there's negligable increase in speed though.

Only 50p extra for a 2port SATA 6Gb/s PCI-E 1x card over the 3Gb/s version from Scan.

 

Not a negligible increase in speed - zero increase in speed!  Every hard drive on the market today is barely fast enough to saturate the bandwidth provided by SATAI.  SATAII is worthwhile in some cases, but SATAIII is pure marketing hype.  It matters if SSDs are involved, but in a HDD-only system it doesn't matter one bit (pun intended!).

Every hard drive on the market today is barely fast enough to saturate the bandwidth provided by SATAI.  SATAII is worthwhile in some cases, but SATAIII is pure marketing hype.  It matters if SSDs are involved, but in a HDD-only system it doesn't matter one bit (pun intended!).

 

When I was benchmarking the Samsung 103's 1TB drives for speed. They were getting 80MB/s write and 160MB/s burst read speeds.  In the cases with those drives, the SATA II did show the potential for those drives.

My benchmarks showed them to be faster then the Seagate 7200RPM 1.5tb's at the time.

 

I say this because in comparison, I tested an SSD on SATA I and it barely broke 100MB/s read yet on a SATA II it hit close to 250MB/s read.

 

Now depending on how large the cache is on the newer drives that come out, The burst to cache can approach pretty fast speeds if there's enough space for the data.

 

Imagine what the Momentus XT hybrids may be capable of when they are available in SATA III speeds.

So can we deduce that if we have at least 1 5400 rpm 2TB data drive then a 2TB parity drive that's 7200 rpm would be pointless? I was going to spend an extra £20 for a 7200 on my parity drive but after reading Rajahal explanation I don't think I'll need to now.  

 

This is not true.

 

If you are writing to an array disk that is a 7200 RPM disk, and your parity disk is 7200 RPM, you will have improved write performance, even if every other data disk in your array is 5400 RPM.

 

But if your parity is 5400 RPM, it wouldn't matter if every data disk was 7200 RPM, you'd still get the slightly slower write performance.

 

As others have said, the slight write performance boost is often not worth the extra cost, extra power consumption, and extra heat generated by the faster spinning disks.  But this is a personal decision for each user.  I personally have a 7200 RPM parity, and a few 7200 RPM data disks for my most frequently updated data.  The rest are 5400 RPM.

 

It also depends on what you store on your file server.  When I used to do massive torrents on my unRAID server, that 7200 Parity drive helped a great deal.  Would it be worth an extra 20 to me. Heck yeah.

 

It's especially important if you have any 7200's in your server and access many small files.

It depends on what you expect. My Hitachi 5k3000 works fine for me. I can drag and drop large files and then do something else while they are moved. Any files I'm accessing for editing or viewing "real-time" will be small enough I can live with any write lags.

 

The SATA port speed will definately help with buffer access times but really won't have much effect once the drive is reading or writing to the platters.

 

Peter