Hi guys.

 

Im new to unRaid, just bought my first plus license.

 

My configuration is Intel DB43LD motherboard with a Celeron E3400 CPU and 2GB 800mhz RAM

My HDD`s are:

1 x WD 2TB Black with 64MB Cache (WD2001FASS-00W2B0)

1 x WD 2TB Green with 64MB Cache (WD20EARS-00MVWB0)

2 x WD 1TB Green with 64MB Cache (WD10EARS-00Y5B1)

 

I did some testS to see the improvment one gets when using Black as parity drive.

The test were on one of the Green 1TB drives which was 70% full, but both testS on black as parity and green as parity were on that same drive with the same cpacity.

 

The results when 2TB Green is parity:

Average copy speed on windows was 32.5 MB/s

CrytalDiskMark 3.0

 

The results when 2TB Black is parity:

Average copy speed on windows was 31.5 MB/s

 

CrytalDiskMark 3.0

 

 

The most important thing for me is copying files, large ones, I do not care about random seeks and stuff like that.

Since the server is intended to stream only media.

I did the test several times, especially the windows copy test which are "Real wold" test for me.

The result are the same all over, which means the black drive gives no improvment in the large file copy area.

 

Is this correct? am I doing something wrong?

 

Also, the black drive dosent seem to be Advanced format, there is noting on google and the sticker dosent mention it...

The green drives are (all of thme) so I put a jumper in 7-8 place.

 

Also, the program used for testing copy in windows uses high precision win api clock to measure the copy length in time and does that 10 times (10 copies) and the results match a single manual explorer copy.

 

Thank you

Shlomi

This is correct, and expected behavior.  A write to the array is only as fast as the slowest disk involved.  Since all your data drives are 5400 rpm green drives, then it makes no difference if you use a faster parity drive or not.

 

It is curious that the green drive as parity results in a slightly faster write.  My guess is that it has something to do with the 7200 rpm and 5400 rpm spindle speeds being out of sync, and so there are a few wasted rotations of the 7200 rpm drive while it spins into the right spot to sync up with the 5400 rpm drive at certain points.  That's just a guess, though.

Thanks...

 

To add a caveat to what I wrote above - there is one situation in which the faster parity drive will help write speeds.  If you are writing multiple simultaneous files to different data drives you should see slightly faster speeds with a 7200 rpm parity drive as compared to a 5400 rpm parity drive.  How much of a difference I don't know exactly, but I doubt it is very worthwhile.  Still, if you have a black drive to use anyway, it may be worthwhile.

 

The other good use for a 7200 rpm drive is as either a cache drive or as a data drive that you use specifically for small and often accessed files (photos, documents, etc).

If you use the 7200 rpm drive as parity, and in the future add a 7200 rpm data disk, writes to that data disk will be a bit faster. If you have a 5400 rpm parity, there is no benefit to adding 7200 rpm drives.