From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: non fs-data and gpt partitioned md Date: Thu, 19 Apr 2012 10:38:23 +1000 Message-ID: <20120419103823.30ca2834@notabene.brown> References: <1334695210.6026.31.camel@hermes> <20120418181833.0581d8ba.kgunders@teamcool.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/_j+s=VelxY/z4Lr0iuCmvFj"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20120418181833.0581d8ba.kgunders@teamcool.net> Sender: linux-raid-owner@vger.kernel.org To: Ken Gunderson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/_j+s=VelxY/z4Lr0iuCmvFj Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 18 Apr 2012 18:18:33 -0600 Ken Gunderson wrote: > On Tue, 17 Apr 2012 14:40:10 -0600 > Ken Gunderson wrote: >=20 > Apologies for following my own post but I guess should elaborate... >=20 > > Hello: > >=20 > > I'm wanting to set up a new md root lvm based configuration and after > > reading various docs am confused about how I should be going about > > this. My intent is to have mirrored /boot and swap partitions and a > > raid10 / partition with LVM. > >=20 > > Issue #1: gpt is recommended over mbr based partitioning for new > > installs, even on BIOS based systems (presuming these BIOS will boot > > gpt, wh/mine do). Auto-assemble is not recommended for new > > installations (my understanding is that it is not necessary with > > initramfs) so I presume I should be specifying partition type DA. > > However, while gdisk et.al. allow for selecting type FD, they do not > > offer DA as an option. >=20 > Per , Linux ignores > partition type codes. Yet per man mdadm: >=20 > "When creating a partition based array, using mdadm with > version-1.x metadata, the partition type should be set to 0xDA (non > fs-data). This type selection allows for greater precision since using > any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)], > might create prob=E2=80=90 lems in the event of array recovery through a = live > cdrom." >=20 > So which is it? Does partition type code matter to md/mdadm or not? Both. Neither.=20 md does handle 0xFD partitions a bit differently, but I recommend not using that feature. Other than that md igores them. mdadm ingores them completely. But other tools - typically installers - might pay some attention to them. Using 0xDA discourages such tools from mishandling them. > =20 > > Issue #2: Is there any reason to prefer 1.0 vs. 1.2 metadata? I can > > use either grub2 or Syslinux boot loaders. My understanding is that > > Syslinux supports the former while Grub2 supports 1.2. All other > > things being equal, I'd prefer to use Syslinux. Unless there is some > > technical reason to favor 1.2 metadata and/or Grub2. > >=20 > > So what would be best practices recommended way to proceed here? >=20 > The reason I ask is that I bring such a configuration online on > Archlinux by following these instructions: >=20 > >=20 > But I'll be damned if I can recover from failed drive simulations - at > least reliably, as sometimes it works while others not - so I'm just > trying to rule out potential variables here. >=20 > Thanks-- Ken >=20 Any reason for preferring one of 1.0 and 1.2 is out side of md. Maybe you want to be able to mount one half of a RAID1 independently. You need 1.0 for that. Maybe you want to ensure that never happens. Then 1.2 = is better. Maybe your boot loaded only works with one. Then the choice is cle= ar. NeilBrown --Sig_/_j+s=VelxY/z4Lr0iuCmvFj Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT49efznsnt1WYoG5AQLZRRAAoXke0BICV9BdtqUxjyWbehfrY+R7latS KWIVG3ItYPWFbNEiNsEmB/jcvTXaOqB01Vg4DDw0JJVMGh8EmF/XKA50ggs+K4AF g1bfmj/Kd7Vh+gV8+emS80EOCesON7hJG1jb7hCwMbFN20JNbhk8vSG8/tGqjl1W oYq8jEgm66kuTIEe/mTseE7qw7w1N3ke1dpzFbvmCL99NfAxXD/K1Op2CFNUq2Bi cOeAl2LKVh5Ri2v0NPsDkLnm4BvZxErqgcYqcUj3VCIzAxL1/emxFFi2EcPe2Q8y KJO1ORDGzSUIeNI7SylsHY9ITQODmOaO/GQbvfIR2X/pFJTLxTETHBHe4wdwfHne L8dWS4eImxidk+SUqsoYih4BdSeekM1b/cZaKMsLBWcnFc54c/z78Lg4/hQCd6cJ Z/rqYC9LVmtlR9dpppDaCrooOgzbKkWssm5bnjo9W4qENnZrjz3OZhciXHEIS0Hn iz7UMJBc5qNiRoBPJ7VoWb2adtTrwDa8eoUWXU0ZSHHf/QWIrcaqnbp5WJVzzP9+ XWZFi1cTSPfGBosZWxVJGtojXRuUoajZhWOqOyVV7nnNv8N7IVP2u4XjO+6xR4fM igmrZOiV0qYn1LaoHnZo2u15NTNNFBcPOd3hkkytfJxQv5wMzBNpZj71WY6nWrl5 i6L3omNgMj4= =uWEx -----END PGP SIGNATURE----- --Sig_/_j+s=VelxY/z4Lr0iuCmvFj--