poweredge,cluster and external shared SCSI device.

Michael_E_Brown@Dell.com Michael_E_Brown at Dell.com
Wed Mar 13 10:21:00 CST 2002


This configuration is not currently tested by Dell under Linux. If you want
support for this kind of configuration, you will have to get it through your
HA product vendor. To my knowledge, no HA vendor supports this configuration
with Dell PERC cards.

But a couple of tips, make sure you flush the block device cache before
moving luns between machines. (For example, for every partition on the disk
that is moving do a: /sbin/blockdev --flushbufs /dev/xxx) Otherwise, if the
lun moves back to the original machine, it may decide to use stale cached
information instead of reading off of the disks. Next thing you know, your
filesystem is completely gone.
--
Michael

> -----Original Message-----
> From: Pierre POMES [mailto:ppomes at reservit.com]
> Sent: Wednesday, March 13, 2002 10:12 AM
> To: Michael_E_Brown at exchange.dell.com
> Cc: linux-poweredge at exchange.dell.com
> Subject: Re: poweredge,cluster and external shared SCSI device.
> 
> 
> Hi Michael,
> 
> Thanks for you answer. I already know the first URL, I read it before
> posting my first message. But I do not want to share an ext2 
> filesystem,
> I want to share RAID logical drives.
> 
> On the first channel of the powervault, I've done the 
> following test: I
> defined two RAID1 drives (in the PERC bios of each node). 
> Each node can
> access theses drives using /dev/sdb and /dev/sdc. On each drive, I
> defined one partition. So finally I can use two filesystems : 
> /dev/sdb1
> and /dev/sdc1.
> 
> In a normal usage, node 1 will mount /dev/sdb1 and node 2 will mount
> /dev/sdc1. Therefore each filesystem is mounted by one node 
> at the same
> time.  In case of failure of one node, the other will mount the 2
> filesystems, until the first comes up again.
> 
> So my real question is: in a two nodes cluster environnment with a
> powervault 210, is it safe to do host based RAID on logical drives,
> assuming that:
> - each logical drive will be accessed by at most one node at the same
> time.
> - the two locical drives are on the same SCSI channel
> 
> It seems to work fine during my tests :
> 1) I can mkfs each filesystem simultaneoulsly (node 1 mkfs /dev/sdb1,
> and node 2 mkfs /dev/sdc1)
> 2) I can copy a huge file (5G) on each filesystem on each node (node 1
> copies to /dev/sdb1, node 2 copies to /dev/sdc1)
> 3) when I umount a filesystem from one node, I can mount it from the
> other.
> 4) And vice-versa....
> 
> But what can really happen ? I don't know if my config is 
> really safe...
> 
> Thanks,
> 
> > 
> > 
> http://lists.us.dell.com/pipermail/linux-megaraid-devel/2001-A
> ugust/000044.h
> > tml
> > http://lists.us.dell.com/cgi-bin/htsearch?words=cluster
> > --
> > Michael
> > 
> > > -----Original Message-----
> > > From: Pierre POMES [mailto:ppomes at reservit.com]
> > > Sent: Wednesday, March 13, 2002 5:26 AM
> > > To: linux-poweredge at exchange.dell.com
> > > Subject: poweredge,cluster and external shared SCSI device.
> > >
> > >
> > > Hi,
> > >
> > > I need to create a linux cluster with two nodes and an 
> external shared
> > > storage. This storage is a Dell Powervalut 210S, 
> controlled by a RAID
> > > device on each host (each node has a PERC3 controller). 
> Each node is a
> > > PowerEdge 2550.
> > >
> > > I would like to create an active/active cluster, one node running
> > > apache,
> > > the other mysql. In case of failure of a node, the other 
> will run the
> > > two services until the first comes up gain.
> > >
> > > I know that since the RAID is done on each node, I cannot 
> create only
> > > one filesystem with the database and the web pages. So I need
> > > to create
> > > two filesystems, one containing the database, the other 
> the web pages.
> > > What is the best to do on the powervault :
> > >
> > > 1) create one RAID logical drive with the two partitions ?
> > > 2) Or create two RAID logical drive with one paritition on each ?
> > >
> > > Do you know if these two solutions can run safely without data
> > > corruptions ? I plan to use redhat 7.2. The advantage of the first
> > > solution is that I need only 3 HD drives for RAID5. With 
> the second
> > > one, with two logical drives I need HD 6 drives for RAID5.
> > >
> > > Do you have some advices ?
> > >
> > > Thanks a lot for your help,
> > > --
> > > Pierre POMES                        mailto:ppomes at reservit.com
> > > Interface Technologies
> > >
> > > _______________________________________________
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> > >
> 
> -- 
> Pierre POMES                        mailto:ppomes at reservit.com
> Interface Technologies
> 




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