Multiple Paths to SAN with LVM in Linux? Post: 302131133

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Special Forums Hardware Filesystems, Disks and Memory Multiple Paths to SAN with LVM in Linux? Post 302131133 by deckard on Thursday 9th of August 2007 09:29:40 AM

08-09-2007

Registered User

Multiple Paths to SAN with LVM in Linux?

I'm setting up a CentOS 5 server that will be connected to an HP EVA4000. My previous experience is with an HP VA7400 and HP-UX. In HP-UX I can add "alternate paths" to a volume group in order to have redundant paths to the SAN via dual fiber channel HBAs just by either adding them with 'vgextend' or appending the appropriate PV paths when using 'vgcreate'. I tried doing something similar in CentOS with 'vgextend' and got some errors about duplicate PV ids. The LUN (a single one) I create on the EVA4000 show up on the CentOS box as /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd. And when I partitioned /dev/sda so that I had /dev/sda1, I also saw that /dev/sdb1, /dev/sdc1 and /dev/sdd1 were automagically there. So I know that these extra devices reflect the dual fiber channel HBAs and the dual paths through our redundant fiber switches.

My question is... did I do this the right way? When I do a 'vgdisplay' now I get:

Code:

[root@localhost ~]# vgdisplay
  Found duplicate PV Up921bgzWK4I7xtw7JiOB3VrdbVZhH2Z: using /dev/disk/by-path/pci-0000:13:00.0-fc-0x50001fe1500ca568:0x0001000000000000-part1 not /dev/sda1
  Found duplicate PV Up921bgzWK4I7xtw7JiOB3VrdbVZhH2Z: using /dev/disk/by-id/scsi-3600508b400070ac40000900000090000-part1 not /dev/disk/by-path/pci-0000:13:00.0-fc-0x50001fe1500ca568:0x0001000000000000-part1

at the beginning of the expected output. I want to avoid having to test the redundancy by disconnecting the fiber if possible. And in all honesty I don't think this is the right way to set up redundant paths on CentOS (or any other Linux distro for that matter). I think the "alternate paths" functionality is specific to HP-UX's implementation of LVM. But I suspect there is a "right way" to do alternate paths on Linux for redundancy.

Last edited by deckard; 08-10-2007 at 11:16 AM.. Reason: Forgot code tags...

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LEARN ABOUT DEBIAN

dpm-addfs

DPM-ADDFS(1)						    DPM Administrator Commands						      DPM-ADDFS(1)

NAME

       dpm-addfs - add a filesystem to a disk pool

SYNOPSIS

       dpm-addfs --poolname pool_name --server fs_server --fs fs_name [ --st status ] [ --weight weight ] [ --help ]

DESCRIPTION

       dpm-addfs adds a filesystem to a disk pool.

       This command requires ADMIN privilege.

OPTIONS

       pool_name
	      specifies the disk pool name previously defined using dpm-addpool.

       server specifies the host name of the disk server where this filesystem is mounted.

       fs     specifies the mount point of the dedicated filesystem.

       status Initial  status  of this filesystem. It can be set to 0 or DISABLED or RDONLY.  This can be either alphanumeric or the corresponding
	      numeric value.

       weight specifies the weight of the filesystem. This is used during the filesystem selection. The value must be positive.  It is recommended
	      to use a value lower than 10. Default is 1.

EXAMPLE

	    dpm-addfs --poolname Volatile --server sehost --fs /data

EXIT STATUS

       This program returns 0 if the operation was successful or >0 if the operation failed.

SEE ALSO

       dpm(1), dpm_addfs(3), dpm-addpool(1)

LCG
								      $Date$							      DPM-ADDFS(1)

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