Hi,
Here is a nice example from one of my RHEL 4 Oracle servers:
We have three layers:
first the LUNs from the SAN are multipathed to device aliases:
[root@ ~]# multipath -ll
sanb (XXXX60e8003f653000000XXXX000001c7)
[size=101 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:1:1 sdb 8:16 [active][ready]
\_ 1:0:1:1 sdd 8:48 [active][ready]
sana (XXXX60e80039cbe000000XXXX000006ad)
[size=101 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:1 sda 8:0 [active][ready]
\_ 1:0:0:1 sdc 8:32 [active][ready]
Next these multipath aliases are RAIDed:
[root@ ~]# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.01
Creation Time : Thu Nov 2 13:07:01 2006
Raid Level : raid1
Array Size : 106788160 (101.84 GiB 109.35 GB)
Device Size : 106788160 (101.84 GiB 109.35 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Thu Dec 28 09:36:19 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Number Major Minor RaidDevice State
0 253 2 0 active sync /dev/mapper/sana
1 253 3 1 active sync /dev/mapper/sanb
UUID : b5ac4ae9:99da8114:744a7ebb:aba6f687
Events : 0.4254576
And finally, the RAID device is used with LVM:
[root@ ~]# vgs -o +devices
VG #PV #LV #SN Attr VSize VFree Devices
vg00 2 2 0 wz--n- 31.78G 0 /dev/cciss/c0d0p2(0)
vg00 2 2 0 wz--n- 31.78G 0 /dev/cciss/c0d0p4(0)
vg00 2 2 0 wz--n- 31.78G 0 /dev/cciss/c0d0p2(250)
vg01 1 5 0 wz--n- 101.84G 0 /dev/md0(0)
vg01 1 5 0 wz--n- 101.84G 0 /dev/md0(5120)
vg01 1 5 0 wz--n- 101.84G 0 /dev/md0(5376)
vg01 1 5 0 wz--n- 101.84G 0 /dev/md0(5632)
vg01 1 5 0 wz--n- 101.84G 0 /dev/md0(8192)
This works very well, as both paths and mirrors are able to break away
without any disruption in disk access.
Cheers,
Christian
<mathias.herzog@p
ostfinance.ch>
Sent by: To
linux-lvm-bounces <linux-lvm@redhat.com>
@redhat.com cc
Subject
28.12.2006 09:12 RE: Mirror between
different SAN fabrics
Please respond to
LVM general
discussion and
development
<linux-lvm@redhat
.com>
> -----Original Message-----
> From: linux-lvm-bounces@redhat.com
> [mailto:linux-lvm-bounces@redhat.com] On Behalf Of Matt P
[...]
> I think the proper way would be to use mdadm. Setup software
> RAID1 prior to getting LVM involved...
That sounds like a good solution. So far I don't know mdadm but I'm
already getting into it
Thanks, Mathias
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