Will a SMR pool slow down a CMR pool?

[mrleaw]

Hello everyone,

I accidentally bought some SMR drives a couple of years ago and am finally replacing them with CMR drives. But as the SMR drives still work, I'd like to make a new pool with them, which I'll use for less important data and where the read/write speeds aren't that important. The only question I have is whether that would impact the performance of the other CMR pool, as they would of course share the ARC. Would there be a significant impact on the CMR pool's performance?

Thanks

 

[Ericloewe]

Simple answer is "no", but SMR may be too painful even under such conditions.

 

[morganL]

Hello everyone,

I accidentally bought some SMR drives a couple of years ago and am finally replacing them with CMR drives. But as the SMR drives still work, I'd like to make a new pool with them, which I'll use for less important data and where the read/write speeds aren't that important. The only question I have is whether that would impact the performance of the other CMR pool, as they would of course share the ARC. Would there be a significant impact on the CMR pool's performance?

Thanks

A 2nd pool is a good isolation.

I expect SMR drives to behave better with Mirror vdevs... reads and writes are larger and less frequent. However, we have not validated that and don't intend to encourage the use of SMR drives.

 

[Etorix]

Better still: Use these SMR drives in a non-ZFS NAS.

 

[Ericloewe]

I don't expect that to be much better either.

 

[joeschmuck]

But as the SMR drives still work

Are you just stating that the SMR drives are operational or are you also stating that they previously were working in TrueNAS as well as still being operational? There is a big difference. If you have not used these in TrueNAS before then I would not recommend you use them and realize that many people have made the mistake of using SMR drives and have lost data. Just sayin'

The only question I have is whether that would impact the performance of the other CMR pool, as they would of course share the ARC.

Previously answered, No. But your SMR pool will have slow write speeds. If you have a large ARC then that should offset some of the write speed operations but it's not a solution for the problems introduced by the SMR drive. The vdev design was already given as an example to use mirrors.