mixing different speed/size HD's in mirrored VDEV's in single pool?

[N123]

Question: I currently have two 18tb 7200 rpm drives and two mirrored 4tb 5400 rpm drives for a TrueNas Scale server.

Performance/stability-wise, is it better to:
(1) only use the two 18tb discs in a single mirror (I don't really need the extra space in the 4tb discs which I would retire for this scenario)
(2) mirror the two 18tb 7200rpm discs as VDEV1 and mirror the two 4tb 5400rpm discs as VDEV2 in the same pool?

I've tried looking through related posts on this and the Truenas forums and haven't found a clear answer.

Thanks in advance,

N123

 

[morganL]

Question: I currently have two 18tb 7200 rpm drives and two mirrored 4tb 5400 rpm drives for a TrueNas Scale server.

Performance/stability-wise, is it better to:
(1) only use the two 18tb discs in a single mirror (I don't really need the extra space in the 4tb discs which I would retire for this scenario)
(2) mirror the two 18tb 7200rpm discs as VDEV1 and mirror the two 4tb 5400rpm discs as VDEV2 in the same pool?

I've tried looking through related posts on this and the Truenas forums and haven't found a clear answer.

Thanks in advance,

N123

2 Mirrors will work...... but performance will be constrained by the slowest mirror.... the 18TB mirror.

 

[N123]

would the 18tb

2 Mirrors will work...... but performance will be constrained by the slowest mirror.... the 18TB mirror.

would the 18tb mirror (7200rpm) be slower than the 4tb mirror (5400rpm)--does this have to do with the size of the disks in the 18tb mirror?

 

[morganL]

would the 18tb

would the 18tb mirror (7200rpm) be slower than the 4tb mirror (5400rpm)--does this have to do with the size of the disks in the 18tb mirror?

Yes speed is really about IOPS per TB..... since the drives are larger, there will be more data on those drives and they become the bottleneck.