Date: Sat, 8 Jun 2013 21:04:44 -0400 From: Chris Ross <cross+freebsd@distal.com> To: "Steven Hartland" <killing@multiplay.co.uk> Cc: fs@freebsd.org Subject: Re: Changing the default for ZFS atime to off? Message-ID: <CA7987A0-2B4B-444D-AE37-FC5E8736C3BB@distal.com> In-Reply-To: <459E2FCADB4E40079066E4ABDBE47AFE@multiplay.co.uk> References: <16FEF774EE8E4100AD2CAEC65276A49D@multiplay.co.uk> <20130608213331.GB18201@icarus.home.lan> <01719722FD8A41B4A4366611972A703A@multiplay.co.uk> <20130609001532.GA21540@icarus.home.lan> <459E2FCADB4E40079066E4ABDBE47AFE@multiplay.co.uk>
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I agree strongly with Jeremy's general opinion. But, am far less =
established
in the community, so only wanted to make a couple of small points.
On Jun 8, 2013, at 20:48 , "Steven Hartland" <killing@multiplay.co.uk> =
wrote:
> I guess where I'm coming from is making better for the vast majority.
>=20
> I believe there's no point in configuring for a rare case by default
> when it will make the much more common case worse.
I think the point being made, and certainly in my mind reading this =
thread,
is that you're considering the "rare" case to be more rare than you =
factually
know it to be, and more importantly (IMO), you're considering "worse" on
something that I consider a very small issue. I understand the reasons =
we
choose to turn off atime (by adding it to the kernel, at the time, in =
1994) at
UUNET for the USENET filesystems. It was just too much activity. But, =
for
a less than 110% active system, and given the relatively small number of =
things
that are accessed far more often than they're updated, I just don't =
think it's that
big of an issue.
And, yes, I'm aware of the flash write issue, and I side with turning =
off there,
though I wouldn't be default. (And, defaulting filesystem parameters =
based on
some impression of the underlying hardware seems risky at best anyway.)
I think there are a small number of cases where it's an issue, and =
those people,
yourself included, already know how to solve the problem. Myself, =
personally,
running only small systems, have never turned off atime updates. Don't =
feel
any need to. For specific heavy-load production systems, _everything_ =
is
looked at with a fine-toothed-comb. No reason to "default" something =
that
only those systems need.
>> All said and done: I do appreciate having this discussion, =
particularly
>> publicly on a list. Too many "key changes" in FreeBSD in the past =
few
>> years have been results of closed-door meetings of sorts (private =
mail
>> or in-person *con meetings), so the fact this is public is good.
>=20
> Everyone has their different uses of any OS, different experience etc,
> so things like this need open discussion IMO.
I agree very much, and while my opinions may not match many others, =
I've
been very pleased to read this discussion. Thank you for bringing it =
up.
- Chris
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