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Discussion Starter · #1 ·
I now have a Hitachi 4TB 5400rpm hdd and a Seagate Barracuda XT 7200rpm. I was told a parity drive for flexraid (or snapRaid, unRaid) should be reliable and fast. In that case, which one should I pick for a parity drive and why? Thank you.
 

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From what I have seen, Hitachi drives are usually more reliable than Seagate. Picking the faster drive for parity isn't always useful if the rest of your drives are slow. Parity calculation in FlexRAID will go as fast as your slowest drive.
 

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That's the total speed ^


I had a good post in my server thread about this topic.


2TB of WD green might be equal to 3 TB or 4TB of a faster drive. It won't matter much.


Just use the largest drive you think you'll use for data drives in future do you not limited.



With 3 and 4TB drives cheap and common today that's the smallest you should use for your parity.


I actually have a 3TB WD green for my parity and I am a notorious basher of those ... Lol


So basically you'll be fine with any choice. Size matters more than speed. Go big.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by amarshonarbangla  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm#post_23260060


From what I have seen, Hitachi drives are usually more reliable than Seagate. Picking the faster drive for parity isn't always useful if the rest of your drives are slow. Parity calculation in FlexRAID will go as fast as your slowest drive.
Thanks for the reply. I think when a parity FAST drive is working (parity calculating) with slower drives, yes, it's slow down, but when it's working with FAST drives as it is, the time for sync, check, .. is obviously reduced. Is that correct?
 

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Quote:
Originally Posted by Mfusick  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm#post_23261992


That's the total speed ^

Yes it is. The total speed is affected by the slowest drive in the array. If all the drives are fast, the total speed will be faster. That's how I understand it.
Quote:
Originally Posted by Elpee  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm#post_23262134


Thanks for the reply. I think when a parity FAST drive is working (parity calculating) with slower drives, yes, it's slow down, but when it's working with FAST drives as it is, the time for sync, check, .. is obviously reduced. Is that correct?

Yup.
 

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Discussion Starter · #7 ·
Thanks, guys.

My current server has 7 x 4TB 7200rpm, 3 x 4TB 5900rpm, 5 x 3TB 7200rpm, and 20 x 2TB 5400rpm data drives.

I just read a pice of advice from XBMC forum:

"...Green or LP (low power) drives – 5400 or 5900 rpm – are often recommended both for parity and data because they are cooler, quieter, and use less power than higher speed drives.

Improved performance can be seen if both the parity drive and the data drives are of a faster rotational speed: having a 7200 rpm parity drive with all 5400 rpm data drives will not be of benefit. There is a compromise – having a 7200 rpm parity drive and one or more 7200 rpm data drives (the drives that will be used most-used) as well as some 5400 rpm data drives. In this case, writes to the 7200 rpm data drives will be faster, and writes to the 5400 rpm data drives will be slower......"

So, I know Hitachie is more reliable but I'll pick a 7200rpm Seagate drive as my parity drive.

Besides, personally I think WD and Seagate have slightly easier RMA processes than Hitachi and that is important when I ask for a replacement for my parity drive.
 

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Quote:
Originally Posted by amarshonarbangla  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm#post_23260060


Picking the faster drive for parity isn't always useful if the rest of your drives are slow. Parity calculation in FlexRAID will go as fast as your slowest drive.

Not sure that's a valid assumption. read is way faster than write, so I would think having a faster write rate (e.g. 7200RPM drives) would still increase performance with 5400RPM DRU's
 

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Quote:
Originally Posted by Elpee  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm#post_23262323


Thanks, guys.

My current server has 7 x 4TB 7200rpm, 3 x 4TB 5900rpm, 5 x 3TB 7200rpm, and 20 x 2TB 5400rpm data drives.

I just read a pice of advice from XBMC forum:

"...Green or LP (low power) drives – 5400 or 5900 rpm – are often recommended both for parity and data because they are cooler, quieter, and use less power than higher speed drives.

Improved performance can be seen if both the parity drive and the data drives are of a faster rotational speed: having a 7200 rpm parity drive with all 5400 rpm data drives will not be of benefit. There is a compromise – having a 7200 rpm parity drive and one or more 7200 rpm data drives (the drives that will be used most-used) as well as some 5400 rpm data drives. In this case, writes to the 7200 rpm data drives will be faster, and writes to the 5400 rpm data drives will be slower......"

So, I know Hitachie is more reliable but I'll pick a 7200rpm Seagate drive as my parity drive.

Besides, personally I think WD and Seagate have slightly easier RMA processes than Hitachi and that is important when I ask for a replacement for my parity drive.
 

 

This is some serious amount of drives (and disk space)! I would go with more than just a single parity drive. I have heard a rule of thumb of having a parity drive for every 4-6 data drives. I am not sure if/how this would scale with your 35 drives though.

_____

Axel
 

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Quote:
Originally Posted by Axel  /t/1470589/parity-drives-for-my-flexraid-server-7200rpm-or-5400rpm/0_100#post_23997950



This is some serious amount of drives (and disk space)! I would go with more than just a single parity drive. I have heard a rule of thumb of having a parity drive for every 4-6 data drives. I am not sure if/how this would scale with your 35 drives though.

_____

Axel

In terms of parity speed- smaller drives and faster drives are good. I like 7200rpm 3TB, and they are faster than 4TB 5900rpm or 4TB 5400rpm significantly at parity times. It's not just the faster spindle speed performance, it's also having to read and write 1TB worth less of data too.
 
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