Date: Thu, 22 Oct 2009 12:49:50 -0500 From: Scot Hetzel <swhetzel@gmail.com> To: Aristedes Maniatis <ari@ish.com.au> Cc: freebsd-current@freebsd.org Subject: Re: gpart, bsdlabel and fdisk Message-ID: <790a9fff0910221049n130c5b00x66071a5a718eb6ab@mail.gmail.com> In-Reply-To: <4AE01342.4000303@ish.com.au> References: <4ADE995A.8080009@ish.com.au> <1256174188.2309.22.camel@balrog.2hip.net> <4ADFCFF3.1030201@ish.com.au> <790a9fff0910220001m3d7df03j127b51d7d0696271@mail.gmail.com> <4AE01342.4000303@ish.com.au>
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On Thu, Oct 22, 2009 at 3:09 AM, Aristedes Maniatis <ari@ish.com.au> wrote: > On 22/10/09 6:01 PM, Scot Hetzel wrote: >> >> http://wiki.freebsd.org/RootOnZFS >> >> If anyone notices a problem with them, either let me know or update >> the wiki page. > > That's very helpful, thanks Scot. It raises some questions: > > * you don't have the instruction to perform "echo 'a 1' | fdisk -f - > /dev/ad4" which Robert recommends > Since I had created the ZFS Root on a disk that already had partions on it, and Windows will mark it's partition active, I didn't need this step for the MBR disk. The GPT disk didn't need it either when I had set it up on a extra harddrive on my laptop. I prefer to use: # gpart set -a active -i 1 ad4 Just to make it so that only gpart is needed to setup the system. > * Robert recommends GPT as the "easiest way to get ZFS on root working". > Your instructions seem to lean more toward MBR "The advantage of using a MBR > disk is that you can still dual boot with other Operating Systems.". Are > there any downsides of using MBR which should be explained? > It wasn't supposed to lean either way. It's just that if you need to boot multiple Operating Systems, then a MBR disk was easier to get configured. Recently, I had found ways to multi boot different Operating Systems on GPT using a Hybrid GPT/MBR scheme. I haven't had time to look to see if gpart can create this kind of disk, and if we have a pmbr, gptboot, or gptzfsboot that can be used to select which Operating System to boot. The other option would be to use GRUB. > * I've seen posts here (sorry I don't have one handy) which recommend to not > put swap on ZFS. Apart from crash dumps are there any other reasons to > prefer one over the other? Your instructions explain both, without giving > much of a guide about why you'd choose one. Is a 'native' swap faster than > one on ZFS? > The reason I choose a swap partition over a ZFS swap VOL is that problems can occur when the ZFS filesystem starts to run out of room. > * you write LOADER_ZFS_SUPPORT=YES to src.conf, while previous instruction > in this thread had it written to make.conf > While make.conf can still be used, it is currently shared between ports and src. src.conf is the new location to place all src build options. > * In order to follow http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/Mirror > will you need to run this from the live CD rather than the first install CD? > > * At the top of the same page you give instructions for creating boot, swap > and zfs partitions. But your instructions give block sizes very specific to > your disks. It would be helpful to have something like: > > gpart add -b 34 -s 128 -t freebsd-boot ad0 (why 34? this is a different > magic number to other magic numbers I've seen suggested) Sector 34 is the first available sector after the Primary GPT Header. See http://en.wikipedia.org/wiki/GUID_Partition_Table for a diagram of the GUID Partition Table Scheme. > gpart add -b 162 -s 8G -t freebsd-swap ad0 (the 8G is more readable than > specifying in sectors) > All the guides I had read regarding creating partitions with gpart had used # sectors instead of specifying the size as 8G. According to Oliver Roberts ZFS guide (see http://www.keltia.net/howtos/zfsboot), in order to create a 512MB swap, you have to double the number to get 1G. > or even > > gpart add -b 162 -s 8G -t freebsd-swap -l swap-ad0 ad0 (the human readable > label appears to be a nice feature of GPT) > Adding a label to the partition is another addition I was going to make, as I have several e-mails from the -CURRENT or -STABLE list that suggest using labels when creating ZFS pool instead of the device names, as it would make replacing drives easier. Scothome | help
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