Hi, Need the forums advice.

What would be a better parity drive. 

The WD Red or the Black for the faster RPM.

Thanks

The Reds.

 

There's no advantage to a 7200rpm parity drive unless all of the drives in your array are that speed.

 

The Reds run cooler; use less power; and have excellent sustained transfer rates.

 

... Just to be sure it's clear:  IF you are buying ALL 7200rpm drives, then the answer is to get a 7200rpm parity drive ... but I assume from your question that you want to know if the parity drive would benefit from 7200rpm speed in an array with Red and/or Green data drives => and the answer to that is No.

 

but I assume from your question that you want to know if the parity drive would benefit from 7200rpm speed in an array with Red and/or Green data drives => and the answer to that is No.

There is an exception to that though...  It will benefit (just a little) IF multiple slower-rotating data drives are being written to at the same time.

 

Otherwise, writing speed to the array is limited by the slowest rotating drive involved.

You didn't say if you ever plan to go above 3T disks; if you know you will go to 4T you may want to put a 4T black in as parity now to save time later when you grow.

 

Personally I did this with a mix of Red 2T/3T and a couple Seagate 3T.

 

 

... Just to be sure it's clear:  IF you are buying ALL 7200rpm drives, then the answer is to get a 7200rpm parity drive ... but I assume from your question that you want to know if the parity drive would benefit from 7200rpm speed in an array with Red and/or Green data drives => and the answer to that is No.

 

Actually I have (12) 2TB Blacks. 8 in my array and 4 precleared and waiting to be added, and (2) 2TB Reds that are on their third preclear pass now. I am just over halfway done copying my files over to the array. And then i'll add the parity drive. Just wanted to know which one to save for parity. Looks like it should be the black.

Thanks to all for your replies.

Actually I have (12) 2TB Blacks. 8 in my array and 4 precleared and waiting to be added, and (2) 2TB Reds that are on their third preclear pass now. I am just over halfway done copying my files over to the array. And then i'll add the parity drive. Just wanted to know which one to save for parity. Looks like it should be the black.

Thanks to all for your replies.

 

In that case, I'd do this:

 

(a)  Don't put the Reds in the array (yet).

(b)  Add one of the Blacks as the parity drive -- then, after it's finished building parity, do a parity check (and time it ... simply note exactly when you started the test -- it will tell you the time it finishes, so computing the time is simply).

 

©  Now add one of the pre-cleared Reds to your array; format it; and then do another parity check -- timing it as well.  All other things being equal, it would take notably longer ... but all other things aren't equal, so that may not be the case.  The Reds have a higher density than the Blacks; so although the Blacks have better seek times, and a higher rotation speed; the Reds have notably higher areal density, as they 1TB/platter units compared to 500MB/platter on the Blacks ... this will largely offset (and perhaps even beat) the higher rotational speed of the Blacks.

 

With the mix of drives you've described, I'd use a Black for parity -- NOT because I expect faster parity checks;  but because it should slightly improve your array write times, since the access to the parity drive will be slightly faster, and there are two access to the parity drive for every write. 

The Reds.

 

There's no advantage to a 7200rpm parity drive unless all of the drives in your array are that speed.

 

The Reds run cooler; use less power; and have excellent sustained transfer rates.

 

Not true.

 

If you happen to be accessing two data disks at the same time then performance IS better with a faster parity disk.

 

I went from a 2TB green to a 2TB Black and I saw not insigificant single and muti-disk write speeds increases!

Agree that for simultaneous writes it would help.  I was thinking more in terms of parity check speeds, where the limiting factor is the slowest drive in use at any given time, so a fast parity drive doesn't really help UNLESS it's the only drive that size ... in which case the "tail" of the parity check would be improved.