[Ocfs2-users] Missing something basic...

[paul fretter (TOC)]

Oops, yes you are correct.

Cheers
Paul

> -----Original Message-----
> From: Sunil Mushran [mailto:Sunil.Mushran at oracle.com]
> Sent: 19 October 2007 17:31
> To: paul fretter (TOC)
> Cc: Randy Ramsdell; ocfs2-users at oss.oracle.com
> Subject: Re: [Ocfs2-users] Missing something basic...
> 
> Actually GFS(2) is also a shared disk clustered filesystem.
> 
> Lustre is a good example of a distributed fs.
> 
> paul fretter (TOC) wrote:
> > I had similar confusion myself when first looking for a suitable
> cluster
> > FS.  I'm not an expert at this, so forgive me if my language appears
> > simplistic.
> >
> > There seemed to be 2 basic species:
> > - There are those which aggregate local storage LUNs from each host
> into
> > a single contiguous 'virtual' device, e.g. RedHat GFS etc.  Bear in
> mind
> > the4se 'local' LUNS could be a local disk, or a dedicated LUN on a
> SAN.
> >
> > - Then there are those which expect all hosts to have direct
(shared)
> > access to the same LUN.
> >
> > OCFS2 falls into the latter category.
> >
> > For disk redundancy you could use a shared disk shelf (e.g. IBM
> DS4xxx),
> > create a RAID(1,4 or 5) set in the hardware and present it as a
> single
> > shared-access LUN.  All your nodes then have a connection to the LUN
> > (e.g. by fibrechannel). In effect it is a small SAN!  OCFS2 is then
> the
> > glue which manages the file locking and metadata so that nodes don't
> try
> > to write to the same blocks at the same time.
> >
> > By creating a "RAID" using multiple OCFS2 volumes you are bringing
> the
> > role of device level redundancy work into the OS, which is
> effectively
> > software RAID and is not conducive to high performance or
> reliability.
> >
> > Then for high availability of the storage, a good way might be to
> create
> > a duplicate shared device and let the hardware perform mirroring for
> you
> > (e.g. over fibrechannel, infiniband, iSCSI) etc, and also let the
> > hardware do the failover for you.
> >
> > So, by using a SAN with hardware RAID and hardware mirroring to a
> second
> > SAN device (with hardware RAID), you can achieve resilience and high
> > availability, leaving OCFS2 blissfully unaware.
> >
> > Hope this helps.
> >
> > Kind regards
> > Paul Fretter
> >
> >
> >> -----Original Message-----
> >> From: ocfs2-users-bounces at oss.oracle.com [mailto:ocfs2-users-
> >> bounces at oss.oracle.com] On Behalf Of Randy Ramsdell
> >> Sent: 18 October 2007 14:00
> >> Cc: ocfs2-users at oss.oracle.com
> >> Subject: Re: [Ocfs2-users] Missing something basic...
> >>
> >> Benjamin Smith wrote:
> >>
> >>> I'm stumped. I'm doing some research on clustered file systems to
> be
> >>>
> >> deployed
> >>
> >>> over winter break, and am testing on spare machines first.
> >>>
> >>> I have two identically configured computers, each with a 10 GB
> >>> partition, /dev/hda2. I intend to combine these two LAN/RAID1
style
> >>>
> >> to
> >>
> >>> represent 10 GB of redundant cluster storage, so that if either
> >>>
> >> machine
> >>
> >>> fails, computing can resume with reasonable efficiency.
> >>>
> >>> These machines are called "cluster1" and "cluster2", and are
> >>>
> >> currently on a
> >>
> >>> local Gb LAN. They are running CentOS 4.4 (recompile of RHEL 4.4)
> >>>
> >> I've set up
> >>
> >>> SSH RSA keys so that I can ssh directly from either to the other
> >>>
> >> without
> >>
> >>> passwords, though I use a non-standard port, defined in ssh_config
> >>>
> >> and
> >>
> >>> sshd_config.
> >>>
> >>> I've installed the RPMs without incident. I've set up a cluster
> >>>
> >> called "ocfs2"
> >>
> >>> with nodes "cluster1" and "cluster2", with the corresponding LAN
IP
> >>> addresses. I've confirmed that configuration changes populate to
> >>>
> >> cluster2
> >>
> >>> when I push the appropriate button in the X11 ocfs2console on
> >>>
> >> cluster1. I've
> >>
> >>> checked the firewall(s) to allow inbound TCP to port 7777
> >>>
> > connections
> >
> >> on both
> >>
> >>> machines, and verified this with nmap. I've also tried turning off
> >>>
> >> iptables
> >>
> >>> completely. On cluster1, I've formatted and mounted partition
> >>>
> >> "oracle"
> >>
> >>> to /meda/cluster using the ocfs2console and I can r/w to this
> >>>
> >> partition with
> >>
> >>> other applications. There's about a 5-second delay when
> >>>
> >> mounting/unmounting,
> >>
> >>> and the FAQ reflects that this is normal. SELinux is completely
> off.
> >>>
> >>> Questions:
> >>>
> >>> 1) How do I get this "oracle" partition to show/mount on host
> >>>
> >> cluster2, and
> >>
> >>> subsequent systems added to the cluster? Should I be expecting a
> >>>
> >> /dev/* block
> >>
> >>> device to mount, or is there some other program I should be using,
> >>>
> >> similar to
> >>
> >>> smbmount?
> >>>
> >>>
> >> As the previous post states, you need a shared storage. A quick and
> >> easy
> >> way to do this is to install iscsi-target on another system
> (target1)
> >> and then use open-iscsi to log into the target you just created.
So
> >> have a  third system that create the shared target. Then on
cluster1
> >> log
> >> into the target to create the ocfs2 cluster FS. At this point, you
> can
> >> mount this target on cluster1. On cluster2, log into the target and
> >> mount as you would normally. Of course you will need the correct
> >> cluster
> >> set up. Now you have two systems mounting the shared storage and
> both
> >> r/w.
> >>
> >> Note: You may be able to do this with just two systems.  Use
> cluster1
> >> as
> >> the iscsi target system and ocfs2. On cluster1 install iscsi-target
> >> software and log into the volume share from cluster1 itself.
> Cluster2
> >> would just log in to the the target as normal.
> >>
> >>
> >>> 2) How do I get this /dev/hda2 (aka "oracle") on cluster1 to
> combine
> >>>
> >> (RAID1
> >>
> >>> style) with /dev/hda2 on cluster2, so that if either host goes
down
> >>>
> > I
> >
> >> still
> >>
> >>> have a complete FS to work from? Am I mis-understanding the
> >>>
> > abilities
> >
> >> and
> >>
> >>> intentions of OCFS2? Do I need to do something with NBD, GNBD,
> ENDB,
> >>>
> >> or
> >>
> >>> similar? If so, what's the "recommended" approach?
> >>>
> >>>
> >>>
> >> Yes you are misunderstanding how ocfs2 works. To use raid for the
> >> described purposes, you must use it on the target1 system mentioned
> >> above. On target1, raid two drives or two partitions and then use
> this
> >> array as the target volume you export to cluster1 and cluster2.
This
> >> way
> >> you have a raid array for data protection and ocfs2 for service
> >> integrity.
> >>
> >>> Thanks,
> >>>
> >>> -Ben
> >>>
> >>>
> >>>
> >> _______________________________________________
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> >> Ocfs2-users at oss.oracle.com
> >> http://oss.oracle.com/mailman/listinfo/ocfs2-users
> >>
> >
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> >