Does FreeBSD start slices at head boundaries?

Rick Miller vmiller at
Fri Jul 6 18:44:53 UTC 2012


>> I think Ryan means partition and not slice?
>> I would not recommend no slices at all, It's deprecated to use
>> "dangerously dedicated disks"
> First of all, it's "dedicated disks", there's nothing dangerous
> related. :-)
> If you are using the MBR approach ("old way"), you can do
> either creating a "DOS primary partition", a slice, which
> then will contain your partitions: a swap partition and
> one or more UFS partitions. So you have ad0s1a, ad0s1b
> and so on.
> When you omit the slice and create the partitions on the "bare
> disk", you have a dedicated layout. FreeBSD will run with
> it without any problem. It _may_ be possible that some
> systems like "Windows" have trouble with this approach,
> but if you're going to use FreeBSD only on that disk, there
> is no danger, no problem. You have ad0a, ad0b and so on.
> If you are using the GPT approach ("new way"), you create
> partitions using a different tool set, setting them to be
> a file system or a swap partition. You end up in ad0p1,
> ad0p2 and so on. Note that those aren't "DOS primary
> partitions" anymore, outdated systems may not properly
> recognize them.
> If you label your partitions (you can do that with both
> approaches), you don't need to deal with device names at
> all.

Thanks for this explanation.

Is there any performance advantage to using a "dedicated disk" layout
over the old way of creating a slice and having your partitions within


> To OP:
> If you omit the slice and just create two partitions (one for
> FS and one for swap), FreeBSD will use this fine. Just make
> sure to set the boot parameters properly. Or simply use the
> GPT-related tools, so you don't have to deal with the question
> at all.

Thanks again for the concise explanation.

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