poweredge,cluster and external shared SCSI device.

Pierre POMES ppomes at reservit.com
Wed Mar 13 10:39:01 CST 2002


Hi Michael,

Thanks for the tips. Last question: is it better to define two logical
drives with one partition in each (the config I explained before) or one
logical drive with two partitions (/dev/sdb1 and /dev/sdb2, always
assuming that one partition will be mounted by one node only at the same
time) ? Perhaps it does not matter...

In other words, Linux RAID with PERC is "partition dependant", or
"logical drive" dependant ? (Sorry, I am not used to work with this kind
of config)

Thanks again,

PS: I will test at least my first configuration with hearbeat for a
mysql/apache cluster (-> failover cluster). 


> 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
> > > >
> > > > _______________________________________________
> > > > Linux-PowerEdge mailing list
> > > > Linux-PowerEdge at dell.com
> > > > http://lists.us.dell.com/mailman/listinfo/linux-poweredge
> > > > Please read the FAQ at http://lists.us.dell.com/faq or search
> > > > the list archives at http://lists.us.dell.com/htdig/
> > > >
> >
> > --
> > Pierre POMES                        mailto:ppomes at reservit.com
> > Interface Technologies
> >
> 
> _______________________________________________
> Linux-PowerEdge mailing list
> Linux-PowerEdge at dell.com
> http://lists.us.dell.com/mailman/listinfo/linux-poweredge
> Please read the FAQ at http://lists.us.dell.com/faq or search the list archives at http://lists.us.dell.com/htdig/

-- 
Pierre POMES                        mailto:ppomes at reservit.com
Interface Technologies




More information about the Linux-PowerEdge mailing list