From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Ledford Subject: Re: [PATCH 0/2] Check node nums for cluster raid Date: Wed, 4 May 2016 11:19:17 -0400 Message-ID: <305eaf9b-1275-f9b9-dae4-1be8f21ed98c@redhat.com> References: <1462350824-9872-1-git-send-email-gqjiang@suse.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nocaWNuDXGJFnBH0pmIELvRPea4X0cPDU" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Jes Sorensen , Guoqing Jiang Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --nocaWNuDXGJFnBH0pmIELvRPea4X0cPDU Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 05/04/2016 11:12 AM, Jes Sorensen wrote: > Guoqing Jiang writes: >> For cluster raid, we do need at least two nodes for it, >> the two patches add the checks before create and change >> bitmap. >> >> Thanks, >> Guoqing =20 >> >> Guoqing Jiang (2): >> Create: check the node nums when create clustered raid >> super1: don't update node nums if it is not more than 1 >> >> Create.c | 7 ++++++- >> super1.c | 5 +++++ >> 2 files changed, 11 insertions(+), 1 deletion(-) >=20 > Hi Guoqing, >=20 > I am a little confused on this one - albeit I haven't looked at it in > detail. Why should it not be possible to start a cluster with one node?= > In theory you should be able to do that, and then add nodes later? Not typically. A single node of a cluster is likely the odd man out, so starting it and allowing changes to the underlying device has a high potential of creating split brain issues. For that reason, most cluster setups require some minimum (usually 2) for a quorum before they will start. Otherwise, given a three node cluster, you could end up with three separate live filesystems and the need to merge changes between them to bring the cluster back into sync. --=20 Doug Ledford GPG KeyID: 0E572FDD --nocaWNuDXGJFnBH0pmIELvRPea4X0cPDU Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBCAAGBQJXKhL1AAoJELgmozMOVy/dxZkP/1+Dma0jfe4Iup5ml2WhH652 cTu5RCPjRuG1ZskHW/p8/4ngCY/i/hJJWOM27l1WDqZ674pgs+CZFQcqq9mX9cWw CeExVr9UBWbYvB7BsLiDwepXBS+MD8wgwLaLE4kMLhL3nvxlg2Xe2c5nCfgTeC3b kMH9e5w0Yaw088qRpN8Y8MTMpAOqUf1AOySxt+p85GuFUr83XrMnviVxyyy+Q8sZ Ldl3tOvut5oW2L+RumrXMxwiA1lLRRYNPk1jBNJPhopGhogkt0OeP2ygnPH3yFn+ WE5BcdkbywcgmNFtTcdvfAZ/89mhu84RWVXTb+OywNca57lc8cWt1EkFXdNHe2bL S6Eyb4pzM2RUe+2ustC7JzuvoKiUTskZ9n66HWt6BjDlKC0FtU7e8557bQ/OQYUb N/b005ZT0eHNM6U9aPlfIYX1mfFb8+SVL10yQ6ZRTj6p8b4alqB6vM0rQDlI47AV fWzi24fD3yBWKDxmKBjKcJIS2ejjCwu7JUXaGXvqEEp1kUvFlTLUCl0B14cmcY0m M7ukSvrCqKE56B3O3jYwQiSuW5oVgt0tRMEqq0zk61acVY631W7o3T6QBhSf32Yc 79OsWGaHLNH4t0VQQ33UBNH7LdUXvbVp+D8eTJpSSD5yHH6kInGUKsCAI9FBM5zL 97GNUIJFjti6H67GI4b6 =ufy/ -----END PGP SIGNATURE----- --nocaWNuDXGJFnBH0pmIELvRPea4X0cPDU--