poweredge,cluster and external shared SCSI device.

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


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-August/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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