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Very low READ speed on new WD 2TB

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June 4, 2010 3:50:03 PM

Hi, Im constantly getting very low read speeds for this drive (~1-2MB/s). I (quick) formated it with default allocation size unit setting for NTFS in Windows XP's Disk Manager. Harddrive is connected to a PCI card with additional SATA connector.

Write speed is OK, in some cases over 50MB/s.

Does anyone know how could I fix that?

More about : low read speed 2tb

a b G Storage
June 4, 2010 5:06:46 PM

Make sure the drive is not running in PIO mode instead of DMA mode.
What else do you have on the PCI bus? It is a shared bus so other components can slow down the drive.
Can you not connect the drive directly to the motherboard?
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a b G Storage
June 4, 2010 5:45:35 PM

Depending on which WD hard drive (you didn't say) it might need the partition re-alligned.
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June 4, 2010 9:04:17 PM

sturm said:
Make sure the drive is not running in PIO mode instead of DMA mode.
I cant find this setting in Device manager for this drive.
What else do you have on the PCI bus? said:
What else do you have on the PCI bus?
Only TV card, PCI sata card has two ports, I tried to connect second hdd (same type), same result.
Can you not connect the drive directly to the motherboard? said:
Can you not connect the drive directly to the motherboard?
No I cant, its old motherboard but it has integrated sata raid on-board controller and hdds connected to it works fine.

MrLinux said:
Depending on which WD hard drive (you didn't say) it might need the partition re-alligned.
This one http://www.wdc.com/en/products/products.asp?DriveID=615

Is it possible only read speed could be affected? I find it quite strange.
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a b G Storage
June 4, 2010 9:24:50 PM

That should be a standard drive (not advanced format) but I'd be tempted to down-load and run the alignment tool anyway; if it isn't needed it won't run.
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June 5, 2010 7:46:33 AM

Yes it says "No ADF drive detected" (which is correct)
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June 5, 2010 10:46:10 AM

When you say 1-2mb/s is that a hard drive benchmark like HDTune? Or is what the speed you get when you drag select a million old files and copy it to your new hard drive?

If you are transfering many small files, random read on most hard disks don't exceed 1-2mb/s depending on how small the files are.

If you are copying many many small files from the drive to itself, then it needs to do a read and write cycle and this can take even longer. Typical of people moving folders with lots of pictures since pictures are very small.


Download HD Tune run it. If you suspect your hard drive is failing, please back up all data.
http://www.hdtune.com/download.html
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June 5, 2010 12:36:41 PM

Its same low speed either i copy small or big files, i have tested this and yes it is same when i copy files from drive to itself too.

Harddrives are new and both write and read speeds are OK if i connect them through USB (adapter).
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a c 363 G Storage
June 5, 2010 3:46:46 PM

Wait. Your last post says the HDD works just fine when connected a different way - via USB adapter - but is too slow when connected to your controller card installed in a PCI slot. Seems top me that points pretty clearly to the controller card, NOT the HDD unit.
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June 5, 2010 4:51:48 PM

Quite possibly.

But how come write speeds are ok, sometimes even peaking at 90MB/s

PCI card uses this chipset http://www.via.com.tw/en/products/peripherals/serial-at... (i dont have hdds in raid)

Any thoughts what or why it should affect specifically reading speed?

(btw, it behaves same in XP and 7)
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a c 363 G Storage
June 5, 2010 7:34:52 PM

Did some kind of driver come with the card? Maybe you should seek out the most recent driver release for the card and your OS.
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June 5, 2010 10:28:04 PM

Yes, driver is up-to-date.

Its bit more complicated.

I connected old 80GB Maxtor SATA drive to it (PCI card with sata controller) and both write and read speed on it is very good, basically as it should, over 50MB/s.

So it looks like some weird compatibility issue with 2TB WD hdds and PCI card. It detects drives without problem though, how does it cause trouble with read speed only is quite a mystery for me..

I wonder if all WD 2TB harddrives would end up with similar results in this configuration.
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a c 415 G Storage
June 5, 2010 11:23:43 PM

Do your PCI card and the hard drive use the same SATA version? SATA is supposed to be upward and downward compatible between versions, but sometimes the drive and the port fail to autonegotiate the speed properly. Most drives have a jumper that can be used to force the drive to the lower speed.
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June 6, 2010 9:08:44 AM

I installed jumper, it didnt help.

I tried to split harddrive to smaller partitions, it didnt help either. (write speed remains very good)

Im running out of ideas. :/ 
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November 6, 2010 6:14:36 PM

hi, have you found any solution ?
i have exactly same problem
doesn´t work under xp, but i tried linux (ubuntu and opensuse) and there it works fine
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November 14, 2010 11:59:29 AM

On Via forum admin says that VT6421 chip does not support larger disks than 750 GB. I was not even able to format 2TB WD EARS caviar (the one with advanced format). Alleged bad sectors are reported as well, but with another non WD 2TB HD although it formatted, also alleged bad sectors appeared, apparently due to the PCI card with Via VT6421 chip, Reading speeds were very erratic.
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a c 127 G Storage
November 14, 2010 1:00:25 PM

Could we see a CrystalDiskMark benchmark?

I/O performance over PCI is crap of course; it's a shared bus. But sequential I/O should still be decent; about 70-80MB/s.
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