From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Huffman Subject: Re: multipath: Determine which device to use for grubdevice.map file Date: Fri, 19 Feb 2010 14:32:52 -0800 Message-ID: <4B7F1194.2040201@storix.com> References: <4B7DE60A.9020805@storix.com> <8F08A56613D77044BD153E2AC5DA0F8403B0E9F0@CORPUSMX40A.corp.emc.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8F08A56613D77044BD153E2AC5DA0F8403B0E9F0@CORPUSMX40A.corp.emc.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids Thanks for the response Wayne, but this does me no good. You cannot use the /dev/disk/by-id/* entries for device.map. You have to use the block device and not a link or dm-* device name. Essentially, I need to know which underlying paths can be written to directly. -David berthiaume_wayne@emc.com wrote: > Hi David. > > For SLES you should be using > /dev/disk/by-id/36006016094511600449d92ae1937d611-part2 for a typical > root partition. > > Regards, > Wayne. > > -----Original Message----- > From: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] > On Behalf Of David Huffman > Sent: Thursday, February 18, 2010 8:15 PM > To: dm-devel@redhat.com > Subject: [dm-devel] multipath: Determine which device to use for > grubdevice.map file > > I need to configure a dm-multipath device (mpatha) as a boot disk in a > script. For RHEL it appears I can put the mpath device in my device.map > file. However, for SLES 11 if I use the mpath device, grub fails with > "Floating point exception". For SLES I have to use the underlying path > device (sd[a-z]). > > I know which devices make up my multipath disk. Here is an example that > shows my problem. > > mpatha (36006016094511600449d92ae1937d611) dm-0 DGC,DISK > [size=50G][features=1 queue_if_no_path][hwhandler=1 emc][rw] > \_ round-robin 0 [prio=2][active] > \_ 2:0:1:0 sdd 8:48 [active][ready] > \_ 3:0:1:0 sdf 8:80 [active][ready] > \_ round-robin 0 [prio=0][enabled] > \_ 2:0:0:0 sdc 8:32 [active][ready] > \_ 3:0:0:0 sde 8:64 [active][ready] > > Out of the 4 paths, only two (sdd and sdf) are active. This output is > not very good to parse through in a script to determine which disks I > can specify in my device.map file. Is there a command or better way to > determine which underlying paths I can use in my device.map file. > > For clarification, here is a breakdown of my device.map entries and the > results: > > (hd0) /dev/mapper/mpatha - FAIL with "Floating point exception" > > (hd0) /dev/sdc - FAIL with "Error 21: Selected disk does not exist" > > (hd0) /dev/sdd - Success!!! > > I would rather put the mpath device in device.map, but that does not > appear to be an option for SLES. Is there a way to determine the > underlying path device that is "active" and not just enabled? > > Right now I can run "dd if=/dev/sdc of=/dev/null bs=512 count=1 > 2>/dev/null; echo $?" > > This will tell me in the device can be written to. Any suggestions would > > be helpful. > > - David > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel > > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel >