FreeBSD's UFS vs Ext4

J65nko j65nko at
Tue Feb 9 01:54:13 UTC 2010

On Mon, Feb 8, 2010 at 5:46 AM, alex <alex at> wrote:

> I do suspect personally that the ext4 filesystem is the reason for the
> difference here, since ext4 has a number of features such as deferred disk
> writes etc. Even deleting a large file off that raid array I can see a
> difference, prior to reformatting, i deleted a 190GB file off the raid,
> under UFS the delete took quite some time (well over 10 seconds), under ext4
> the deletion of the same size file took about 3 seconds.
> But what I said with ext4 being faster then the aging UFS still rings true
> in my mind, look at the recent Phoronix benchmarks for yourself and see (10
> pages of benchmarks).
> (skip to page 7 of the benchmarks if you want to see the I/O stuff relating
> to disk performance)

According to the first page they used the default configuration of all
benchmarked OS'es.
And what is the default mount option on Linux "async"

The FreeBSD man page for mount describes this "async" option as follows:

async   All I/O to the file system should be done asynchronously.
        This is a dangerous flag to set, since it does not guar-
        antee that the file system structure on the disk will
        remain consistent.  For this reason, the async flag
        should be used sparingly, and only when some data recov-
        ery mechanism is present.

The OpenBSD man page has the following additional remark:

        The most common use of this flag is to speed up
        restore(8) where it can give a factor of two speed in-

Conclusion: you cannot compare filesystem performance, when you give
one a unfair speed advantage of what could be a factor two.

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