Re: Softdep and noatime
On Tue, Dec 03, 2019 at 11:25:23AM GMT, Stuart Henderson wrote: > On 2019-11-30, Raymond, David wrote: > > I am switching to OpenBSD from Linux and I have questions about the > > use of softdep and noatime in mounting disks. I have a variety of > > systems with a mix of SSDs and rotating disks. > > > > Softdep seems to have some advantages in speeding file access, but it > > is not the default. Are there any downsides in using softdep? > > Yes, that's why it's not on by default. Uses more memory, delays freeing > space when removing files, tends to cause a kernel panic if the drive > goes unresponsive (which the drive might have otherwise recovered from > after a delay). It's not that much of an improvement with SSDs anyway, > it's most useful with drives that are slow at random writes (higher > seek times). > > > On SSDs in particular, is it worth setting noatime to reduce the > > number of disk writes? > > In general, not really unless your drives are slow, or you often do > reads across a large set of files and don't have anything that cares > about access times on those files. > I second that - an old Asus Eee PC got quite usable once I've enabled softdep. I don't enable it on anything else any more, though. Regards, Raf
Re: Softdep and noatime
On 2019-11-30, Raymond, David wrote: > I am switching to OpenBSD from Linux and I have questions about the > use of softdep and noatime in mounting disks. I have a variety of > systems with a mix of SSDs and rotating disks. > > Softdep seems to have some advantages in speeding file access, but it > is not the default. Are there any downsides in using softdep? Yes, that's why it's not on by default. Uses more memory, delays freeing space when removing files, tends to cause a kernel panic if the drive goes unresponsive (which the drive might have otherwise recovered from after a delay). It's not that much of an improvement with SSDs anyway, it's most useful with drives that are slow at random writes (higher seek times). > On SSDs in particular, is it worth setting noatime to reduce the > number of disk writes? In general, not really unless your drives are slow, or you often do reads across a large set of files and don't have anything that cares about access times on those files.
Re: Softdep and noatime
On 2019-12-02, Steve Litt wrote:
> I mount everything noatime because I don't care at all about access
> time, I care about modification time.
Access time can be useful in forensics and debugging ("when was program
X last used? when was this file last opened?") but often you won't know
until after the event that you might find it useful.
I tend to use noatime on things like /usr/src, /usr/ports, /cvs but
otherwise leave atimes on as done by default.
Re: Softdep and noatime
On Sat, 30 Nov 2019 18:10:37 +0100 Tomasz Rola wrote: > On Sat, Nov 30, 2019 at 06:12:42AM -0700, Raymond, David wrote: > [...] > > On SSDs in particular, is it worth setting noatime to reduce the > > number of disk writes? > [...] > > I wonder what other will say about this, but I mount everything as > noatime, since more than a decade, spinning or not. I assume this may > make lifetime a bit longer and decided it is better to be on safe(r) > side. > I mount everything noatime because I don't care at all about access time, I care about modification time. SteveT Steve Litt November 2019 featured book: Manager's Guide to Technical Troubleshooting Second edition http://www.troubleshooters.com/mgr
Re: Softdep and noatime
On 2019-11-30 08:12, Raymond, David wrote: > I am switching to OpenBSD from Linux and I have questions about the > use of softdep and noatime in mounting disks. I have a variety of > systems with a mix of SSDs and rotating disks. > > Softdep seems to have some advantages in speeding file access, but it > is not the default. Are there any downsides in using softdep? it's more complicated, and thus, will have more bugs. My personal experience: I'd trust softdep more than any modern Linux filesystem, BUT its still more complicated, and thus will have more bugs than the default FFS. > On SSDs in particular, is it worth setting noatime to reduce the > number of disk writes? Nothing to do with SSDs, as your quest to minimize writes on SSDs is demonstrated stupid and pointless. SSDs fail much more often for reasons other than write fatigue, Optimizing for write fatigue is like protecting your ship against icebergs hitting the propeller. VERY VERY few applications use atime, and yet, it requires an update to the directory for EVERY SINGLE ACCESS. Ouch. So, it's a non-trivial performance gain if you turn it off. That's a great reason to turn it off. Not SSDs. HOWEVER...if you don't need performance and you can't point to a real benefit, as always, keep it on the default. Nick.
Re: Softdep and noatime
On Sat, Nov 30, 2019 at 09:20:37PM +0100, Xianwen Chen (陈贤文) wrote: > Dear Mr. Rola, > > > I wonder what other will say about this, but I mount everything as > > noatime, since more than a decade, spinning or not. I assume this may > > Do you mount swap as noatime too, I'm curious? > > Yours sincerely, > Xianwen Hello, Frankly, I have never considered atime or noatime option for swap. I think there is not much use for atime in swap anyway. Access time for memory pages, this is another story. I guess some optimisation algorithms make use of this information. Ok, so not "everything", I only mount filesystems as noatime. :-) -- Regards, Tomasz Rola -- ** A C programmer asked whether computer had Buddha's nature. ** ** As the answer, master did "rm -rif" on the programmer's home** ** directory. And then the C programmer became enlightened... ** ** ** ** Tomasz Rola mailto:tomasz_r...@bigfoot.com **
Re: Softdep and noatime
On 30.11.2019 14:12, Raymond, David wrote: I am switching to OpenBSD from Linux and I have questions about the use of softdep and noatime in mounting disks. I have a variety of systems with a mix of SSDs and rotating disks. Softdep seems to have some advantages in speeding file access, but it is not the default. Are there any downsides in using softdep? https://www.openbsd.org/faq/faq14.html#SoftUpdates plus 'man mount' option softdep: (FFS only) Mount the file system using soft dependencies. Instead of metadata being written immediately, it is written in an ordered fashion to keep the on-disk state of the file system consistent. This results in significant speedups for file create/delete operations. This option is ignored when using the -u flag and a file system is already mounted read/write. The options async and softdep are mutually exclusive. On SSDs in particular, is it worth setting noatime to reduce the number of disk writes? Why would you want to do that? Are you using it in other OS? Then why and where did you get that idea? Dave Raymond
Re: Softdep and noatime
Dear Mr. Rola, > I wonder what other will say about this, but I mount everything as > noatime, since more than a decade, spinning or not. I assume this may Do you mount swap as noatime too, I'm curious? Yours sincerely, Xianwen
Re: Softdep and noatime
On Nov 30 06:12:42, david.raym...@nmt.edu wrote: > On SSDs in particular, is it worth setting noatime to reduce the > number of disk writes? noatime is worth setting on filesystems where you don't care about atime (a mail client might care about the atime of your /var/mail/mbox, for instance). SSD has nothing to do with it. Treat it as a disk, which it is.
Re: Softdep and noatime
Hello, david.raym...@nmt.edu (Raymond, David), 2019.11.30 (Sat) 14:12 (CET): > I am switching to OpenBSD from Linux and I have questions about the > use of softdep and noatime in mounting disks. I have a variety of > systems with a mix of SSDs and rotating disks. > > Softdep seems to have some advantages in speeding file access, but it > is not the default. Are there any downsides in using softdep? > > On SSDs in particular, is it worth setting noatime to reduce the > number of disk writes? The most recent thread on that topic that I could find: https://marc.info/?t=15181182685 Marcus
Re: Softdep and noatime
On Sat, Nov 30, 2019 at 06:12:42AM -0700, Raymond, David wrote: [...] > On SSDs in particular, is it worth setting noatime to reduce the > number of disk writes? [...] I wonder what other will say about this, but I mount everything as noatime, since more than a decade, spinning or not. I assume this may make lifetime a bit longer and decided it is better to be on safe(r) side. -- Regards, Tomasz Rola -- ** A C programmer asked whether computer had Buddha's nature. ** ** As the answer, master did "rm -rif" on the programmer's home** ** directory. And then the C programmer became enlightened... ** ** ** ** Tomasz Rola mailto:tomasz_r...@bigfoot.com **
