Re: XFS and sector size on thin volumes

[Gionatan Danti <g.danti@assyoma.it>]

Il 16-09-2017 20:33 Eric Sandeen ha scritto:
> 
> 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")?

Thanks.

-- 
Danti Gionatan
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