[Linux-cluster] Storage Cluster Newbie Questions - any help with answers greatly appreciated!

[Kaloyan Kovachev]

Hello,

On Sun, 14 Mar 2010 22:28:20 -0700, Michael @ Professional Edge LLC wrote
> Kaloyan,
> 
> I agree - disabling the qla2xxx driver (Qlogic HBA) from starting at 
> boot would be the simple method of handling the issue.  Then I just put 
> all the commands to load the driver, multipath, mdadm, etc... inside 
> cluster scripts.
> 
> Amusingly it seems I am missing something very basic - as I can't seem 
> to figure out how to not load the qla2xxx driver.
> 
> Do you happen to know the syntax to make the qla2xxx driver not load at 
> boot automatically?
> 
> I've been messing with /etc/modprobe.conf - and mkinird - but no 
> combination has resulted in the - qla2xxx being properly disabled during 
> boot - I did accomplish making one of my nodes unable to mount it's root 
> partition - but I don't consider that success. :-)
> 

Is 'blackist scsi_transport_fc' not enough? What other modules are loaded? If
you blacklist the one, that most others depend on they should not load.

> As for your 2nd idea; I have seen folks doing something similar in that 
> mode; when the disks are local to the node.  But in my case - all nodes 
> - can already see all LUNs - so I dont really have any need to do an 
> iSCSI export - appreciate the thought though.
> 

The idea was actually not to export them, but to run mdamd simultaneously on
both nodes. But the problem is when just one of the nodes looses its link, to
just one of the arrays

> -Michael
> 
> Kaloyan Kovachev wrote, On 3/4/2010 10:28 AM:
> > On Thu, 04 Mar 2010 09:26:35 -0800, Michael @ Professional Edge LLC wrote
> >    
> >> Hello Kaloyan,
> >>
> >> Thank you for the thoughts.
> >>
> >> You are correct when I said - "Active / Passive" - I simply meant that I
> >> had no need for "Active / Active" - and floating IP on the NFS share
> >> would be exactly what I had in mind.
> >>
> >> The software raid - of any type, raid1,5,6 etc... is the issue.  From
> >> what I have read - mdadm - is not cluster aware... and... since all
> >> disks are seen by all RHEL nodes. - As Leo mentioned; some method to
> >> disable the kernel from finding detecting and attempting to assemble all
> >> the available software raids - is a major problem.  This is why I was
> >> asking if perhaps - CLVM w/mirroring would be a better method.  Although
> >> since it was just introduced in RHEL 5.3 - I am a bit leery.
> >>
> >>      
> > I am not common with FC, so maybe completely wrong here, but if you do not
> > start multipath and load your HBA drivers on boot, how the FC disks based
> > software raid will start at all?
> >
> > even if started you may still issue 'mdadm --stop /dev/mdX' in S00 as
> > suggested from Leo and assemble it again as a cluster service later
> >
> >    
> >> Sorry for being confusing - yes - the linux machines will have a
> >> completely different filesystem share; than the windows machines.  My
> >> original thought was I would do "node#1 primary nfs share (floating
> >> ip#1) to linux machines w/node#2 backup" - and then "node#2 primary nfs
> >> or samba share (floating ip#2) to windows machines w/node#1 backup".
> >>
> >> Any more thoughts you have would be appreciated... as my original plan
> >> with MDADM w/HA-LVM - so far doesn't seem very possible.
> >>
> >>      
> > Then there are two services each with its own raid array and ip, but basically
> > the same
> >
> > another idea ... not using it in production, but i had good results (testing)
> > with (small) software raid5 array from 3 nodes ... Local device on each node
> > exported via iSCSI and software RAID5 over the imported ones which is then
> > used from LVM. Weird, but worked and the only problem was that on every reboot
> > of any node the raid is rebuilt, which i won't happen in your case as you will
> > see all the disks in sync (after the initial sync done on only one of them)
> > ... you may give it a try
> >
> >    
> >> -Michael
> >>
> >> Kaloyan Kovachev wrote, On 3/4/2010 8:52 AM:
> >>      
> >>> Hi,
> >>>
> >>> On Wed, 03 Mar 2010 11:16:07 -0800, Michael @ Professional Edge LLC wrote
> >>>
> >>>        
> >>>> Hail Linux Cluster gurus,
> >>>>
> >>>> I have researched myself into a corner and am looking for advice.  I've
> >>>> never been a "clustered storage guy", so I apologize for the potentially
> >>>> naive set of questions.  ( I am savvy on most other aspects of networks,
> >>>> hardware, OS's etc... but not storage systems).
> >>>>
> >>>> I've been handed ( 2 ) x86-64 boxes w/2 local disks each; and ( 2 )
> >>>> FC-AL disk shelves w/14 disks each; and told to make a mini NAS/SAN (NFS
> >>>> required, GFS optional).  If I can get this working reliably then there
> >>>> appear to be about another ( 10 ) FC-AL shelves and a couple of Fiber
> >>>> Switches laying around that will be handed to me.
> >>>>
> >>>> NFS filesystems will be mounted by several (less than 6) linux machines,
> >>>> and a few (less than 4) windows machines [[ microsoft nfs client ]] -
> >>>> all more or less doing web server type activities (so lots of reads from
> >>>> a shared filesystem - log files not on NFS so no issue with high IO
> >>>> writes).  I'm locked into NFS v3 for various reasons.  Optionally the
> >>>> linux machines can be clustered and GFS'd instead - but I would still
> >>>> need to come up with a solution for the windows machines - so a NAS
> >>>> solution is still required even if I do GFS to the linux boxes.
> >>>>
> >>>> Active / Passive on the NFS is fine.
> >>>>
> >>>>          
> >>> Why not start NFS/Samba on both machines with only the IP floating between
> >>> them then?
> >>>
> >>>
> >>>        
> >>>> * Each of the ( 2 ) x86-64 machines have a Qlogic dual HBA 1 fiber
> >>>> direct connected to each shelf  (no fiber switches yet - but will have
> >>>> them later if I can make this all work); I've loaded RHEL 5.4 x86-64.
> >>>>
> >>>> * Each of the ( 2 ) RHEL 5.4 boxes - used the 2 local disks w/onboard
> >>>> fake raid1 = /dev/sda - basic install so /boot and LVM for the rest -
> >>>> nothing special here (didn't do mdadm basically for simplicity of /dev/sda)
> >>>>
> >>>> * Each of the ( 2 ) RHEL 5.4 boxes can see all the disks on both shelves
> >>>> - and since I don't have Fiber Switches yet - at the moment there is
> >>>> only 1 path to each disk; however as I assume I will figure out a method
> >>>> to make this work - I have enabled multipath - and therefore I have
> >>>> consistent names to 28 disks.
> >>>>
> >>>> Here's my dilemma.  How do I best add Redundancy to the Disks, removing
> >>>> as many single points of failure, and preserving as much diskspace as
> >>>> possible?
> >>>>
> >>>> My initial thought was - to take "shelf1:disk1 and shelf2:disk1" and put
> >>>> them into a software raid1 - mdadm; then put the resulting /dev/md0 into
> >>>> a LVM.  When I need more diskspace, I just then create "shelf1:disk2 and
> >>>> shelf2:disk2" as another software raid1 then just add the new "/dev/md1"
> >>>> into the LVM and expand the FS. This handles a couple things in my mind:
> >>>>
> >>>> 1. Each shelf is really a FC-AL so it's possible that a single disk
> >>>> going nuts could flood the FC-AL and all the disks in that shelf go poof
> >>>> until the controller can figure itself out and/or the bad disk is removed.
> >>>>
> >>>> 2. Efficient I am retaining 50% storage capacity after redundancy - if I
> >>>> can do the "shelf1:disk1 + shelf2:disk2" mirrors; plus all bandwidth
> >>>> used is spread across the 2 HBA fibers and nothing goes over the TCP
> >>>> network.  Conversely DRBD doesn't excite me much - as I then have to do
> >>>> both raid in the shelf (probably still with MDADM) and then I add TCP
> >>>> (ethernet) based RAID1 between the nodes - and when all is said and done
> >>>> - I only the have 25% of storage capacity still available after redundancy.
> >>>>
> >>>> 3. I easy to add more diskspace - as each new mirror (software raid1)
> >>>> can just be added to an existing LVM.
> >>>>
> >>>>
> >>>>          
> >>> You may create RAID1 (between the two shelfs) over RAID6 (on the disks from
> >>> the same shelf), so you will loose only 2 more disks per shelf or about 40%
> >>> storage space left, but more stable and faster. Or several RAID6 arrays with
> >>> 2+2 disks from each shelf - again 50% storage space, but better performance
> >>> with the same chance for data loss like with several RAID1 ... the resulting
> >>> mdX you may add to LVM and use the logical volumes
> >>>
> >>>
> >>>        
> >>>>      From what I can find messing with Luci (Conga) though... is - I don't
> >>>> see any resource scripts listed for - "mdadm" (on RHEL 5.4) - so would
> >>>> my idea even work  (I have found some posts asking for a mdadm resource
> >>>> script but I've seen no response)?  I also see with RHEL 5.3 LVM has
> >>>> mirrors that can be clustered now - is this the right answer?  I've done
> >>>> a ton of reading but everything I've dug up so far; assumes that the
> >>>> fiber devices are being presented by a SAN that is doing the redundancy
> >>>> before the RHEL box sees the disk... or... there are a ton of examples
> >>>> of where fiber is not in the picture and there are a bunch of locally
> >>>> attached hosts presenting storage onto the TCP (ethernet) - but I've not
> >>>> found nearly anything on my situation...
> >>>>
> >>>> So... here I am... :-)  I really just have 2 nodes - who can both see -
> >>>> a bunch of disks (JBOD) and I want to present them to multiple hosts via
> >>>> NFS (required) or GFS (to linux boxes only).
> >>>>
> >>>>
> >>>>          
> >>> if the Windows and Linux data are different volumes it is better to
leave the
> >>> GFS partition(s) available only via iSCSI to the linux nodes
participating in
> >>> the cluster and not to mount it/them locally for the NFS/Samba shares,
but if
> >>> the data should be the same you may go even Active/Active with GFS over
iSCSI
> >>> [over CLVM and/or] [over DRBD] over RAID and use NFS/Samba over GFS as a
> >>> service in the cluster. It all depends on how the data will be used from the
> >>> storage
> >>>
> >>>
> >>>        
> >>>> All ideas - are greatly appreciated!
> >>>>
> >>>> -Michael
> >>>>
> >>>> --
> >>>> Linux-cluster mailing list
> >>>> Linux-cluster at redhat.com
> >>>> https://www.redhat.com/mailman/listinfo/linux-cluster
> >>>>
> >>>>          
> >>>        
> >