Register for the iXsystems Community to get an ad-free experience and exclusive discounts in our eBay Store.

Recommended topology for a "fusion" pool?

Yorick

Neophyte Sage
Joined
Nov 4, 2018
Messages
1,231
Interesting. Unexpected, and interesting.
 

Patrick M. Hausen

Neophyte Sage
Joined
Nov 25, 2013
Messages
1,446
Hmmm ... for me that was precisely what I expected.

1st it is inherited like almost any other ZFS attribute.
2nd the docs say:

This value represents the threshold block size for including small file blocks into the special allocation class. Blocks smaller than or equal to this value will be assigned to the special allocation class while greater blocks will be assigned to the regular class.

So if I set special_small_blocks=4k, I fully expect all blocks <= 4k to end up on the special vdev.

I thought that was the point ;)
Patrick
 

Yorick

Neophyte Sage
Joined
Nov 4, 2018
Messages
1,231

Patrick M. Hausen

Neophyte Sage
Joined
Nov 25, 2013
Messages
1,446
Well, maybe I misjudged the evidence and it was just metadata piling up on the SSD.
Unfortunately I cannot test more at the moment - at least not with actual hardware. All systems productive now.
 

Patrick M. Hausen

Neophyte Sage
Joined
Nov 25, 2013
Messages
1,446
@Yorick You are probably right and I interpreted my tests wrongly. I could not reproduce the assumed distribution of zvols with a testpool, stock FreeBSD 12.1 and the OpenZFS port.
 
Top