From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: clustered MD - beyond RAID1 Date: Tue, 22 Dec 2015 09:03:09 +1100 Message-ID: <8737uv4fz6.fsf@notabene.neil.brown.name> References: <56742652.5040304@nasa.gov> <87si2w66tm.fsf@notabene.neil.brown.name> <567850C4.30108@bnl.gov> <87bn9j4jhr.fsf@notabene.neil.brown.name> <56786EA4.2020209@bnl.gov> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Return-path: In-Reply-To: <56786EA4.2020209@bnl.gov> Sender: linux-raid-owner@vger.kernel.org To: Tejas Rao , Scott Sinno , linux-raid@vger.kernel.org Cc: "Knister, Aaron S. (GSFC-606.2)[COMPUTER SCIENCE CORP]" List-Id: linux-raid.ids --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Tue, Dec 22 2015, Tejas Rao wrote: > GPFS guarantees that only one node will write to a linux block device=20 > using disk leases. Do you have a reference to documentation explaining that? A few moments searching the internet suggests that a "disk lease" is much like a heart-beat. A node uses it to say "I'm still alive, please don't ignore me". I could find no evidence that only one node could hold a disk lease at any time. NeilBrown > Only a node with a disk lease has the right to submit= =20 > I/O and disk leases expire every 30 secs and needs to be renewed. Lustre= =20 > and other distributed file systems have other ways of handing this. > > Using md devices in a shared/clustered environment is something not=20 > supported by Redhat on RHEL6 or RHEL7 kernels, so this is something we=20 > would not try in our production environments. > > Tejas. > > On 12/21/2015 15:47, NeilBrown wrote: >> On Tue, Dec 22 2015, Tejas Rao wrote: >> >>> What if the application is doing the locking and making sure that only 1 >>> node writes to a md device at a time? Will this work? How are rebuilds >>> handled? This would be helpful with distributed filesystems like >>> GPFS/lustre etc. >>> >> You would also need to make sure that the filesystem only wrote from a >> single node at a time (or access the block device directly). I doubt >> GPFS/lustre make any promise like that, but I'm happy to be educated. >> >> rebuilds are handled by using a cluster-wide lock to block all writes to >> a range of addresses while those stripes are repaired. >> >> NeilBrown > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJWeHcdAAoJEDnsnt1WYoG5v6EP/jT8//MkxBu4cVvPFw1e7LbW swUFVVPGSFIZE/pWVLIMD7mukO0A2H8Fx4j73lECJ/ozO+mMrDwCfU8Z5UPV+zYy LTod7tgJhL57mLxINQuqhRSR0Zvhzr0tgXZ0HrgncjmResqphyDvA6SUUNwsX7ev 5ovPJtRpBkV8CyHhgU/HXCAJnjUnFY+oa9oKHIqjAVMrc97Nxze36AK6gZZSTDtf wehkSu0jTXoL9EGghTBlXjlecKMpGkid+mHRKjgol4rupK6bNKC1bZnTFOCwvifT fntjcxIETi+UIc5wyckViUOyzh0Al1WZGquCFeG6rEnCTSUs8xAvL1fzCT5ao8/v Q/bqN6DmGv5/K+KsiawsCeFhcW8TshRIc8Z9pOKF/3kVid81bDtxUR8lBE4Jptu2 tkVuAV1FYdWQNPWE2hpBa9vwUVq/HstAkC1z6KLzwD1zIzY8Ia5AU10O/1MnzeJm Oe2BSCLQX4QSJpGHN2MAqPAwnJzqHhshCpB1tU7clXNP7wbjckfWNgmNrbhXrZfp 4rMmvIwRgrDOKgmw4Q0GBZgwhu3PaMAyYUxGs1PdTyiL7G8nE9mOgnIbSm68bkTR TjhgU1626pstKAxx2w2W4L8es398xqKyO9C6+lFNhvi3C9/vntQaUIISdJnFZ5Y7 qI9NUTzHGvLHMLYCKS23 =Ji3L -----END PGP SIGNATURE----- --=-=-=--