RFC: deprecate allocation roundup size

Jeremy Allison jra at samba.org
Tue Jun 18 16:09:07 UTC 2019


On Tue, Jun 18, 2019 at 04:43:58PM +0200, Björn JACKE via samba-technical wrote:
> Hi,
> 
> I was debugging a problem with strict allocate = yes and our current default of
> "allocation roundup size", which is 1MB. While I understand that a large
> allocation roundup size was supposed to the a performance tuning for old SMB1
> clients, this has the side effect that with "strict allocate = yes" this makes
> even small files take at least 1MB on the disk, because smbd allocates that
> ammount of disk space which is given back by smb_roundup. This is an issue for
> some setups, because the extra ammount of needed disk space can be huge
> actually.
> 
> To work around the issue, I tested to remove the smb_roundup in places wherere
> disk space allocation is being done so that the allocation roundup size value
> is only used to announce this 1MB "block size" to the clients. I'm not sure if
> there can be other negative side effect thought if we announce that large block
> size but behave with the actual space allocation with out normal small block
> size.
> 
> As this performance trick is not needed for modern SMB clients any more, it
> might also be be better idea to just reset the value of "allocation roundup
> size" to 4k again, deprecate the option and remove it with one of the next
> releases completely to behave more windows standard conforming and to just cut
> off this source of irritation.

+1 from me and I was the person who added it, a *long* time ago :-).

I agree, I don't think we need this anymore.

Cheers,

	Jeremy.



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