Ubuntu – Is it worth to tune Ext4 with noatime

ext4filesystemperformance

With previous versions of Ubuntu (using Ext3 filesystem) I used to tune it for better performance with noticeable results by setting the noatime parameter in /etc/fstab.

Is it still worth it to do that with the Ext4 filesystem, which is now default in Ubuntu?
If so, does the procedure changed in some way?

An example of this tuning can be found here.

Best Answer

On Ubuntu 10.04, relatime is part of the default mount options, unless overridden in /etc/fstab. The previous few releases had relatime explicitly in /etc/fstab. relatime gives the same speed (and flash write cycle conservation) benefits as noatime, without causing trouble to old-fashioned mail notifiers.

The article you cite recommends data=writeback. Ubuntu defaults to data=ordered. Ubuntu's setting is slower in case of heavy disk load, but carries significantly less risk of data loss in case of a crash or power failure. So I would not recommend changing from the Ubuntu default.

Changing commit=5 to commit=100 increases the time window during which data will be lost in case of a crash, for little benefit in most circumstances.

Summary: leave the settings as they are, they were chosen for a reason.

ADDED: There are other things beyond mount options than can make a difference. Switching from ext3 to ext4 is itself often a visible improvement. Here are a few more tips for laptop users.

If you have a slow SSD, check out this thread at SU. The important tips are to use tmpfs for /tmp and for the browser cache (and perhaps history).
If you have a hard disk and you want it to stop spinning for extended lengths of time, then install noflushd, which allows the disk to spin down by delaying all writes until the RAM is full. (Of course, reads can cause the disk to spin up; you'll want to get into the habit of running cat /files/I/m/likely/to/need >/dev/null before the disk spins down.) In order for noflushd to be effective, turn off all swap and mount your filesystems with something like commit=3600.

Using noflushd effectively means that your data can remain unwritten to disk for an extended length of time. This is a risk, to be weighed against the benefit of not having any noise or heat coming from the disk for a while. Don't use noflushd if you're not comfortable with that risk.

Related Solutions

Ubuntu – How to make noatime mounts default

The kernel used to have a config option for whether to use ATIME or RELATIME; dunno if that also included some option for NOATIME. In any case, that's gone now.

I studied util-linux as well, to see if the mount command had configurable defaults or could be modified, but it did not appear to be the case.

However, it looks like you can patch the kernel to change the default behavior. Modify ./fs/namespace.c, around lines 2334:

long do_mount(...)
...
    /* Default to relatime unless overriden */
    if (!(flags & MS_NOATIME))
            mnt_flags |= MNT_RELATIME;
...

Swap that around:

long do_mount(...)
...
    /* Default to noatime unless overriden */
    if (!(flags & MS_RELATIME))
            mnt_flags |= MNT_NOATIME;
...

And that should do it.

Ubuntu – the default behaviour of atime

From man mount:

Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts.

cat /proc/mounts

Shows that relatime is an option for almost all filesystem mounted, but I can't say for sure if is a default for every filesystem that supports atime.

Best Answer

Related Solutions

Ubuntu – How to make noatime mounts default

Ubuntu – the default behaviour of atime

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