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Oddly low HDD speeds - please help

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November 7, 2010 8:19:22 PM

I recently completed building a home theater server which has 6 SATA 2TB drives made by Western Digital (WD20EVDS). I was surprised that these were a little slow - running about 80MBPs on a SATA3 channel.

Passmark shows:
Sequential Read 95.4 MBPs
Sequential Write 93.3 MBPs
Random Read + write 2.36 MBPs

I was a little shocked. So I went out and for comparison got one of what was called on this sight the fastest drive in the world. The WD2001FASS

Now mind you when I tested this drive it's connected via eSATA but don't think that should make that much of a difference.

Results from Passmark show:
Sequential Read 101.8 MBPs
Sequential Write 88.5 MBPs
Random Read + write 2.85 MBPs

Virtually identical! And the WD2001FASS was supposed to have a max sustained speed nearing 136MPs.

What gives here? Is there something amiss on my motherboard that's causing this? I can't understand why the world's fastest drive is 40% slower than advertised and virtually the same as the drives I have now.

Any tips or ideas would be greatly appreciated.
Thanks

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a c 415 G Storage
November 7, 2010 9:31:39 PM

First of all, the WD20EVDS is a "green" drive that spins at a slower speed. It won't have as fast a transfer rate as a "black" drive.

I don't know how Passmark arrives at its score, but you also need to remember that hard drive transfer rates vary a lot as the head moves from the outermost to the innermost tracks. If Passmark shows the average speed across all tracks then it will be considerably slower than the peak sustained transfer rate at the outermost tracks (which of course is the rate the drive manufacturers like to quote).

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a b G Storage
November 8, 2010 12:35:34 AM
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You shouldn't expect a hard drive to sustain average speed anywhere near its maximum speed. Average speed depends on what you're transfering, where it is on the drive, etc.

Also, as long as you're dealing with spinning, 7200 RPM drives, you won't find a great difference between a "slow" one and a "fast"one.

Your drive is indeed fast, just not as fast as a raid array or an SSD would be. I don't mean to disappoint you, but I feel you had your hopes too high.

You may also consider that the software you are using to benchmark your drives is not the one used on the review, and may not explore the strengths of your newest HDD.
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a b G Storage
November 8, 2010 1:32:58 AM

Is this a NAS using UTP or you just share the main computer and connect the WD20EVDS and WD2001FASS using USB cables?
It's good to use a NAS on a home network sharing files.
Some mobo limits the USB speed only to the first USB for compatibility with legacy hardware. Please check your BIOS manual for this USB speed setting. The second USB is backwards compatible, but their are few things thats need the issue forced, so some board manufacturers include the option.
November 8, 2010 1:39:51 AM

Thanks both for the responses. One important thing I may have overlooked is that since this is a dedicated media host, it is very disk intensive with streaming Blu-ray and h.264 content to multiple endpoints.

Would a RAID array really improve speed even on my current drives? If so, I assume RAID5?

I should also note that when moving content from one drive to another on my current drives I'm getting about 78MBPs but performing the same task using the new drive it drops to around 21MBPs.
November 8, 2010 1:42:58 AM

dEAne said:
Is this a NAS using UTP or you just share the main computer and connect the WD20EVDS and WD2001FASS using USB cables?
It's good to use a NAS on a home network sharing files.
Some mobo limits the USB speed only to the first USB for compatibility with legacy hardware. Please check your BIOS manual for this USB speed setting. The second USB is backwards compatible, but their are few things thats need the issue forced, so some board manufacturers include the option.

All my drives are in one box connected via SATA cables. There are no USB attached drives. The newer drive is attached by eSATA only because I only have 6 drive slots in my htpc case
a c 415 G Storage
November 8, 2010 2:40:58 AM

BluRay only requires less than 5MByte/sec max. If the software buffers intelligently then you should be able to serve several streams simultaneously from a single drive without any problems.
November 9, 2010 3:05:35 PM

I guess I need to look at what services are sucking up disk cycles, like the media foundation.

I still don't understand the whole drive speed thing. I used the exact same test software on both drives, so that variable is removed. Based on what I've seen for performance, the new drive is going back to the store. :( 
November 15, 2010 11:03:20 PM

Best answer selected by the_sentinal.
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