Which drive sees more action Parity vs Data

[Join]

Hello, to start off with im still quite new to software raid and unraid. 

I have three drives, one of which is a Ironwolf Pro, and the others wd reds. I think that it would be best to use the ironwolf pro with longer warrenty and faster rpm as my parity drive. 

I assume that the parity drive receives more writes than the data disc, and would in turn mean that the more durable hdd can take a better "beating", to optimize the lifetime of all three drives? 

Do you guys know more or have experience in this topic?


Regards Fish

[JorgeB]

27 minutes ago, Join said:

I assume that the parity drive receives more writes than the data disc

Yes, everything written to the array updates parity, so if for example you have 10 data disks parity will end up having 10 times the writes of the data disks.

[JonathanM]

Conversely, if you use your server as many do, where a file is written once and read many times, only the write effects parity, reads are done only from the data drive. So the only time the parity drive is read is during parity checks or emulation and rebuild operations.

 

So, the question is, how are you going to use your server? The usage will determine which drives would be optimal for which positions.

[Join]

Interesting, both good and valid points, it did not make my choice any easier. Its going to be alot more writes in the begining at least, and growing. But mostly its static storage so mostly reads and some docker containers and my labservers wil my cachedrives. 

1 hour ago, jonathanm said:

the question is, how are you going to use your server? The usage will determine which drives would be optimal for which positions.

 

9 hours ago, JorgeB said:

Yes, everything written to the array updates parity, so if for example you have 10 data disks parity will end up having 10 times the writes of the data disks.

 

[JonathanM]

1 minute ago, Join said:

it did not make my choice any easier.

LOL. That was my intention. It's not a clear cut situation.

 

I'll add another factor to the equation. Parity doesn't hold any sensible data by itself, it works in conjunction with all the data drives in the parity array. So assuming one parity drive, if one drive fails it is emulated by the rest of the drives, if 2 drives fail, you lose the data on both failed drives. If that happens, you are much better off if parity is one of the failed drives, as it doesn't have any data.

 

So using that info, parity should be the lowest priority for reliability, highest speed for writing, and data drives should be high priority for reliability and read speed.

 

Bottom line, it doesn't make a whole lot of difference in the large scheme, do whatever makes you feel best.

 

Expected lifetime of a drive is a crapshoot not likely to be influenced by whether it's a parity or data drive.

 

Personally I've had better luck with WD than Seagate, so my suggestion is put the Seagate as parity. Since I've only personally had experience with 100's of drives vs. hundreds of thousands manufactured, my statistical experience is meaningless, you do you.