On 07/11/2013 21:14, Todor Petkov wrote:
Hello,
I have IBM Storwize V3700 storage, connected to 2 IBM x3550 M4 servers via fiber channel. The servers are with QLogic ISP2532-based 8Gb Fibre Channel to PCI Express HBA cards and run Centos 5.10
When I export a volume to the servers, each of them sees the volume twice, i.e /dev/sdb and /dev/sdc, with the same size.
Previously I have installed many systems with IBM DS3500 series of storage and the servers see one disk per export. I am using the MPP drives from this package: http://support.netapp.com/NOW/public/apbu/oemcp/apbu_lic.cgi/public/apbu/oem...
I came upon the IBM site, saying to configure multipath (I never did it for DS3500 series). When I did, a new device came, /dev/dm-7, but my goal is to have one /dev/sdX type of device and no device mapper. I read that Storwize support DMP RDAC, and DS support MPP RDAC, but does anyone else have experience with such setup and can give an advice/hint?
Thanks in advance. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
I's been a while since I set this up, and this on on XIV, not v3700 (which we also have but it only has VMware connected to it) but this is a RHEL 5.10 box, so is reasonably compatible.
This is, IMO, normal behaviour for a multipath device. For example on one of our boxes if I run: [root@server ~]# multipath -ll mpath0 (20017380011ea0c74) dm-2 IBM,2810XIV [size=224G][features=1 queue_if_no_path][hwhandler=0][rw] _ round-robin 0 [prio=1][active] _ 3:0:0:1 sdb 8:16 [active][ready] _ 3:0:1:1 sdc 8:32 [active][ready] _ 3:0:2:1 sdd 8:48 [active][ready] _ 3:0:3:1 sde 8:64 [active][ready] _ 3:0:4:1 sdf 8:80 [active][ready] _ 3:0:5:1 sdg 8:96 [active][ready] _ 4:0:0:1 sdh 8:112 [active][ready] _ 4:0:1:1 sdi 8:128 [active][ready] _ 4:0:2:1 sdj 8:144 [active][ready] _ 4:0:3:1 sdk 8:160 [active][ready] _ 4:0:4:1 sdl 8:176 [active][ready] _ 4:0:5:1 sdm 8:192 [active][ready]
You can see there are 12 sdx devices, but that all maps to just 1 LUN. With multipathd installed and running this all maps to a single volume under /dev/mpath/mpath0 which I then use LVM to manage:
--- Physical volume --- PV Name /dev/mpath/mpath0 VG Name vg_data PV Size 224.00 GB / not usable 4.00 MB Allocatable yes (but full) PE Size (KByte) 4096 Total PE 57343 Free PE 0 Allocated PE 57343 PV UUID GY4ekC-KuXE-LyW6-kiHB-F9g6-ivB2-BD01Ih
This all works fine and allows us to loose paths to the SAN with out disruption to the servers. There is no reason to be using /dev/sdx devices to control your underlying hardware, and is in fact coincided bad practice as there is no assurance that when the server next boots it will detect the hardware in the same order. You should really be using UUIDS or device labels to address your storage as that is immutable between boots.
Tris
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