On 9/16/17 2:59 PM, Gionatan Danti wrote:

Il 16-09-2017 20:33 Eric Sandeen ha scritto:

quoted

I don't think I said that - this is the first time you've mentioned
/alignment/, and I've seen no indication of your alignment one way or
another.




that specifies a 4k block size, which is already the default.

You're conflating a lot of issues here - log alignment, sector size,
physical & logical block size presented by both the underlying
storage and the zvol ...

I cannot speak to zvols, as I have no experience with them.

But if the underlying storage is 512e/4k then you may want to specify
the 4k /sector/ size with -s size=4k.

-Eric

Hi Eric, you are right: I messed up the terminology. Sorry for the noise.

I was really speaking about *sector* size. In short, when using ZVOL the physical disk's sector size is not directly announced to the higher layer filesystem. This, in turn, cause mkfs.xfs to automatically select a 512B sector size, even when running on top of 512e/4Kn disks.

From previous emails/threads, I was under impression that XFS sector size only very marginally affect performance. It that true? Can I stick with default mkfs settings? Or should I manually select 4K sector size ("-s size=4k")?

If you have 512/4k disks and mkfs is not defaulting to 4k sector size,
use "-s size=4k"

-Eric