Replacement drive: different brand/model, but matching specs ok?

[bajaking]

Dumb sanity check question:
Our now 5-yr-old v9.3 (!) build on a Supermicro CSE-836E16-R1200B has two raidz-2 pools, spanning 16 of these:
Seagate 6TB ST6000NM0024 SATA 6GB/s 7200RPM 128MB Cache 3.5" HDD

I've always been told "use identical drives - same everything all the time - or everything will fail!". Now, I can order a few Seagates with the same model number but it will take days or more to arrive. But one drive just died, and of course the spares we bought with the build all disappeared, so I'm eager to get at least the failed drive replaced ASAP.
I can pick up (today!) a WD with the same speed and cache, for example:
https://www.centralcomputer.com/p-D...nternal-35in-hard-drive-128mb-dram-cache.html

Am I asking for big trouble with a mix-n-match of drive brands?
Besides size, which hdd specs are critical to match across the system?
I imagine it's not a bad idea to exceed current specs with an eye toward future expansion/updates; am I wrong?
I imagine it's a terrible idea to go with lower specs to save money; am I wrong?

 

[Jailer]

Am I asking for big trouble with a mix-n-match of drive brands?

No it's perfectly fine.

Besides size, which hdd specs are critical to match across the system?

Spindle speed for consistent performance but that's still not a deal breaker. The pool will perform at the speed of the slowest disk.

I imagine it's not a bad idea to exceed current specs with an eye toward future expansion/updates; am I wrong?

Perfectly fine but the larger drive will appear the same size as the smallest drive in the vdev.

I imagine it's a terrible idea to go with lower specs to save money; am I wrong?

What exactly do you mean by lower specs?

 

[bajaking]

Thanks, Jailer, your responses confirmed my own thoughts. Going shopping.

What exactly do you mean by lower specs?

You address spindle speed above, but I was also thinking cache, which I assume would be similar to spindle speed, i.e. a 64MB cache on one disk would introduce a bottleneck, but still work?
I also kind of meant transfer speed, but purely hypothetically since I wouldn't even know where to get something <6GB/s nor if transfer speeds can even be mixed within a system; I'd guess a 3GB/s transfer speed -- if such a disk could be used -- would similarly cause the rest of the system (or just its parent zpool?) to act like 3GB/s.

 

[Jailer]

You address spindle speed above, but I was also thinking cache, which I assume would be similar to spindle speed, i.e. a 64MB cache on one disk would introduce a bottleneck, but still work?
I also kind of meant transfer speed, but purely hypothetically since I wouldn't even know where to get something <6GB/s nor if transfer speeds can even be mixed within a system; I'd guess a 3GB/s transfer speed -- if such a disk could be used -- would similarly cause the rest of the system (or just its parent zpool?) to act like 3GB/s.

None of that will be consequential for proper operation.

 

[joeschmuck]

@Jailer was of course spot on.

The only real limitation is the drive must be equal or larger in capacity. A drive that is smaller will not be able to create the new partitions of the proper size, it doesn't matter how much data you have on the NAS. Always use a Swap File and that gives you a buffer for a drive that is very slightly smaller (in MB).

Hope your shopping goes well. Maybe next time lock up your spare drives to keep others from taking them. Also, if you think you will be growing the pool, this is a good time to use a larger hard drive, once all in the vdev have been replaced then the pool will expand.

Cheers,
-Joe