Date: Mon, 08 Jan 2024 20:39:06 -0600 From: robert@rrbrussell.com To: freebsd-current@freebsd.org Subject: Re: noatime on ufs2 Message-ID: <2eabfb91-afc3-47f7-98b9-1a1791ae6e7d@app.fastmail.com> In-Reply-To: <CAGMYy3vsSD7HHtGxYXJn%2Busr8GCOd-0Xe1crs-Nx=qw-bYJ6HA@mail.gmail.com> References: <ZZqmmM-6f606bLJx@int21h> <CAGMYy3vsSD7HHtGxYXJn%2Busr8GCOd-0Xe1crs-Nx=qw-bYJ6HA@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--54b92331b9ec41dc9f02046dfeeac9b9
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable
On Mon, Jan 8, 2024, at 14:41, Xin LI wrote:
>=20
>=20
> On Sun, Jan 7, 2024 at 5:27=E2=80=AFAM void <void@f-m.fm> wrote:
>> Hi,
>>=20
>> Does /var/mail still need atime?
>>=20
>> I've installed a ufs2-based -current main-n267425-aa1223ac3afc on
>> rpi4/8BG which installs into one / . If it's mounted with noatime,
>> will it have consequences for /var/mail ?
>=20
> It doesn't matter if you don't normally receive emails locally (nowada=
ys, it's rare).
>=20
> If you do receive emails locally, it depends on what application(s) th=
at you are using. Most applications nowadays check both mtime and atime=
plus sizes of the mailbox file and do not rely on atime (because they s=
aved the previous mtime). Without atime updates, some application may c=
laim that you have new mail when the mailbox is not empty when they firs=
t start.
>=20
> That's said, if I were you and I'm using some flash based storage (wit=
h rpi it's highly likely) regardless if I'm using mail locally; most of =
the time the data is not really useful for anything, and it does increas=
e the wear of your storage.
>=20
> This reminds me that -- we probably should have implemented the Linux =
"relative atime" (update atime iff (atime <=3D mtime || atime <=3D ctime=
) || atime is older than a day) and "no diratime" (don't update director=
y atime) for UFS and make the "relatime" option the default; I had an in=
complete implementation about a decade ago somewhere but with the recent=
VFS changes it's probably easier to start over. IMHO, updating atime e=
very time when a file is accessed is not really providing useful data (l=
ike who accessed the file, etc.) for audit purposes and does come with p=
erformance (more write I/O) and reliability (wear of SSD and other flash=
devices) cost, therefore not generally useful in modern days. The Linu=
x relative atime is a pretty clever idea that has covered the most usefu=
l use case for atime (Did I accessed the file after it was last modified=
) and also provided a coarse-grained update (capped to daily, which is a=
reasonable compromise) to the atime.
>=20
> Cheers,
On the Linux side of things I think almost of the mail handling programs=
have migrated to either using MailDir or MH style mailboxes, which don'=
t need atime, for anything local. The MDA/MTA configuration examples hav=
e all used MailDir for around a decade now.
Why not make noatime the default across the whole system? Outside of mbo=
x why is recording access time actually useful?
--54b92331b9ec41dc9f02046dfeeac9b9
Content-Type: text/html;charset=utf-8
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div>On Mon, Jan 8, =
2024, at 14:41, Xin LI wrote:<br></div><blockquote type=3D"cite" id=3D"q=
t" style=3D""><div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"qt-gmail_d=
efault" style=3D"font-family:monospace, monospace;"><br></div></div><div=
><br></div><div class=3D"qt-gmail_quote"><div dir=3D"ltr" class=3D"qt-gm=
ail_attr">On Sun, Jan 7, 2024 at 5:27=E2=80=AFAM void <<a href=3D"mai=
lto:void@f-m.fm" target=3D"_blank">void@f-m.fm</a>> wrote:<br></div><=
blockquote class=3D"qt-gmail_quote" style=3D"margin-top:0px;margin-right=
:0px;margin-bottom:0px;margin-left:0.8ex;border-left-width:1px;border-le=
ft-style:solid;border-left-color:rgb(204, 204, 204);padding-left:1ex;"><=
div>Hi,<br></div><div> <br></div><div> Does /var/mail still need atime?<=
br></div><div> <br></div><div> I've installed a ufs2-based -current main=
-n267425-aa1223ac3afc on<br></div><div> rpi4/8BG which installs into one=
/ . If it's mounted with noatime,<br></div><div> will it have consequen=
ces for /var/mail ?<br></div></blockquote><div><br></div><div class=3D"q=
t-gmail_default" style=3D"font-family:monospace, monospace;">It doesn't =
matter if you don't normally receive emails locally (nowadays, it's rare=
).<br></div><div class=3D"qt-gmail_default" style=3D"font-family:monospa=
ce, monospace;"><br></div><div class=3D"qt-gmail_default" style=3D"font-=
family:monospace, monospace;">If you do receive emails locally, it depen=
ds on what application(s) that you are using. Most applications no=
wadays check both mtime and atime plus sizes of the mailbox file and do =
not rely on atime (because they saved the previous mtime). Without=
atime updates, some application may claim that you have new mail when t=
he mailbox is not empty when they first start.<br></div><div class=3D"qt=
-gmail_default" style=3D"font-family:monospace, monospace;"><br></div><d=
iv class=3D"qt-gmail_default" style=3D"font-family:monospace, monospace;=
">That's said, if I were you and I'm using some flash based storage (wit=
h rpi it's highly likely) regardless if I'm using mail locally; most of =
the time the data is not really useful for anything, and it does increas=
e the wear of your storage.<br></div><div class=3D"qt-gmail_default" sty=
le=3D"font-family:monospace, monospace;"><br></div><div class=3D"qt-gmai=
l_default" style=3D"font-family:monospace, monospace;">This reminds me t=
hat -- we probably should have implemented the Linux "relative atime" (u=
pdate atime iff (atime <=3D mtime || atime <=3D ctime) || atime is=
older than a day) and "no diratime" (don't update directory atime) for =
UFS and make the "relatime" option the default; I had an incomplete =
;implementation about a decade ago somewhere but with the recent VFS cha=
nges it's probably easier to start over. IMHO, updating atime =
;every time when a file is accessed is not really providing useful data =
(like who accessed the file, etc.) for audit purposes and does come with=
performance (more write I/O) and reliability (wear of SSD and other fla=
sh devices) cost, therefore not generally useful in modern days. T=
he Linux relative atime is a pretty clever idea that has covered the mos=
t useful use case for atime (Did I accessed the file after it was last m=
odified) and also provided a coarse-grained update (capped to daily, whi=
ch is a reasonable compromise) to the atime.<br></div><div class=3D"qt-g=
mail_default" style=3D"font-family:monospace, monospace;"><br></div><div=
class=3D"qt-gmail_default" style=3D"font-family:monospace, monospace;">=
Cheers,<br></div></div></div></blockquote><div dir=3D"ltr"><div class=3D=
"qt-gmail_quote"><div class=3D"qt-gmail_default" style=3D"font-family:mo=
nospace, monospace;"><br></div><div class=3D"qt-gmail_default" style=3D"=
font-family:monospace, monospace;">On the Linux side of things I think a=
lmost of the mail handling programs have migrated to either using MailDi=
r or MH style mailboxes, which don't need atime, for anything local. The=
MDA/MTA configuration examples have all used MailDir for around a decad=
e now.<br></div></div><div><br></div><div>Why not make noatime the defau=
lt across the whole system? Outside of mbox why is recording access time=
actually useful?<br></div></div><div><br></div></body></html>
--54b92331b9ec41dc9f02046dfeeac9b9--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?2eabfb91-afc3-47f7-98b9-1a1791ae6e7d>