Date: Mon, 8 Jan 2024 14:12:06 -0700 From: Warner Losh <imp@bsdimp.com> To: Xin LI <delphij@gmail.com> Cc: freebsd-current@freebsd.org Subject: Re: noatime on ufs2 Message-ID: <CANCZdfpf0k4od%2B1_cNDiKR=HPwMZ0GsWhH9O6yRi=F72BwJRDg@mail.gmail.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
--0000000000001888a4060e75a716 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Jan 8, 2024 at 1:41=E2=80=AFPM Xin LI <delphij@gmail.com> wrote: > > > On Sun, Jan 7, 2024 at 5:27=E2=80=AFAM void <void@f-m.fm> wrote: > >> Hi, >> >> Does /var/mail still need atime? >> >> 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 ? > > > It doesn't matter if you don't normally receive emails locally (nowadays, > it's rare). > > If you do receive emails locally, it depends on what application(s) that > you are using. Most applications nowadays check both mtime and atime plu= s > sizes of the mailbox file and do not rely on atime (because they saved th= e > previous mtime). Without atime updates, some application may claim that > you have new mail when the mailbox is not empty when they first start. > > That's said, if I were you and I'm using some flash based storage (with > 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 increase the > wear of your storage. > > 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 directory atim= e) > for UFS and make the "relatime" option the default; I had an > incomplete implementation about a decade ago somewhere but with the recen= t > VFS changes it's probably easier to start over. IMHO, updating atime eve= ry > time when a file is accessed is not really providing useful data (like wh= o > accessed the file, etc.) for audit purposes and does come with performanc= e > (more write I/O) and reliability (wear of SSD and other flash devices) > cost, therefore not generally useful in modern days. The Linux relative > atime is a pretty clever idea that has covered the most useful use case f= or > 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. > I like that compromise. It will miss a lot, but that 'miss' results in atime being good to only about a day, which for the vast majority of things is fine. Warner > Cheers, > --0000000000001888a4060e75a716 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">= <div dir=3D"ltr" class=3D"gmail_attr">On Mon, Jan 8, 2024 at 1:41=E2=80=AFP= M Xin LI <<a href=3D"mailto:delphij@gmail.com">delphij@gmail.com</a>>= wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px = 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir= =3D"ltr"><div dir=3D"ltr"><div style=3D"font-family:monospace,monospace"><b= r></div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmai= l_attr">On Sun, Jan 7, 2024 at 5:27=E2=80=AFAM void <<a href=3D"mailto:v= oid@f-m.fm" target=3D"_blank">void@f-m.fm</a>> wrote:<br></div><blockquo= te class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px = solid rgb(204,204,204);padding-left:1ex">Hi,<br> <br> Does /var/mail still need atime?<br> <br> I've installed a ufs2-based -current main-n267425-aa1223ac3afc on<br> rpi4/8BG which installs into one / . If it's mounted with noatime,<br> will it have consequences for /var/mail ?</blockquote><div><br></div><div s= tyle=3D"font-family:monospace,monospace">It doesn't matter if you don&#= 39;t normally receive emails locally (nowadays, it's rare).</div><div s= tyle=3D"font-family:monospace,monospace"><br></div><div style=3D"font-famil= y:monospace,monospace">If you do receive emails locally, it depends on what= application(s) that you are using.=C2=A0 Most applications nowadays check = both mtime and atime plus sizes of the mailbox file and do not rely on atim= e (because they saved the previous mtime).=C2=A0 Without atime updates, som= e application may claim that you have new mail when the mailbox is not empt= y when they first start.</div><div style=3D"font-family:monospace,monospace= "><br></div><div style=3D"font-family:monospace,monospace">That's said,= if I were you and I'm using some flash based storage (with 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 increase the wear = of your storage.</div><div style=3D"font-family:monospace,monospace"><br></= div><div style=3D"font-family:monospace,monospace">This reminds me that -- = we probably should have implemented the Linux "relative atime" (u= pdate atime iff (atime <=3D mtime || atime <=3D ctime) || atime is ol= der than a day) and "no diratime" (don't update directory ati= me) for UFS and make the "relatime" option the default; I had an = incomplete=C2=A0implementation about a decade ago somewhere but with the re= cent VFS changes it's probably easier to start over.=C2=A0 IMHO, updati= ng atime=C2=A0every time when a file is accessed is not really providing us= eful data (like who accessed the file, etc.) for audit purposes and does co= me with performance (more write I/O) and reliability (wear of SSD and other= flash devices) cost, therefore not generally useful in modern days.=C2=A0 = The Linux relative atime is a pretty clever idea that has covered the most = useful use case for atime (Did I accessed the file after it was last modifi= ed) and also provided a coarse-grained update (capped to daily, which is a = reasonable compromise) to the atime.</div></div></div></blockquote><div><br= ></div><div>I like that compromise. It will miss a lot, but that 'miss&= #39; results in atime being good to only about a day, which for the vast ma= jority of things is fine.=C2=A0</div><div><br></div><div>Warner</div><div>= =C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0= .8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"l= tr"><div class=3D"gmail_quote"><div style=3D"font-family:monospace,monospac= e">Cheers,</div></div></div> </blockquote></div></div> --0000000000001888a4060e75a716--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CANCZdfpf0k4od%2B1_cNDiKR=HPwMZ0GsWhH9O6yRi=F72BwJRDg>