Date: Wed, 14 Nov 2012 23:10:04 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freebsd-questions@freebsd.org Subject: Re: Advanced Format Drive ? Message-ID: <alpine.BSF.2.00.1211142250370.58597@wonkity.com> In-Reply-To: <17388.1352953630@tristatelogic.com> References: <17388.1352953630@tristatelogic.com>
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On Wed, 14 Nov 2012, Ronald F. Guilmette wrote: > I'm looking at the examples section of the gpart(8) man page. May I > assume that if I just want to merely ``try out'' GPT... you know... > taking it out on the road for a first time test run... that I can > just do the first five (5) commands listed under EXAMPLES and then > that will be enough to go ahead and try installing FreeBSD into the > created freebsd-ufs partition? > > Even assuming that the answer is yes, I have still more questions... > Where are these magic numbers coming from?? I am specifically talking > about the number "34" in the "-b 34" option and also the number "162" > in the "-b 162" option. Tha man page just tosses those into the example > command lines without saying a word about them. And you can probably > guess what it is that is especially troubling to me about them... neither > one of them is divisible by 8 (i.e. 4KB/512B). So would the examples > in the current gpart(8) man page produce an Epic Fail when and if they > were used with a modern "Advanced Format" drive? -b is the beginning block of a partition. 34 is a magic value, the size of a standard GPT partition table. A good overall reference on GPT is the Wikipedia page: http://en.wikipedia.org/wiki/GUID_Partition_Table Remember that the man page is a reference, not a tutorial. I wanted more specific notes that followed best practices, and that was the source for this article: http://www.wonkity.com/~wblock/docs/html/disksetup.html In general, you create a "partition scheme" first. This can be MBR, GPT, or others. (But use GPT.) Rather than combine the bootcode with the partition table, GPT just uses a small partition for it. Since the standard GPT allows for up to 128 partitions, there's no reason not to use them. Next come other partitions for UFS or ZFS filesystems or swap. That's it, really. The rest is details the man page can explain, like additional options for alignment. (The creation of the first UFS partition in the article does not use -a because older versions of gpart did unexpected things when -a and -b were combined. The alignment produced is correct.)
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