How to change disk sequence on DELL R900 with LINUX

[Thomas Fess]

Yes, I understand.  
What I am saying is that Linux doesn't work that way.
Your /boot will alwasy be in the same place physically and (swap, / ) but the device name will change due to the time the OS sees the device.  So whichever disk/device is up/availiable first gets /dev/sda (if it's scsi)  What you need to do is get the scsi LUN ID or SCSI device ID and map or setup using that ID# and not the /dev/sd?  That ID will never change for that disk / lun / device whatever

Example:
 
What you currently use:
 
/etc/fstab output ->
 
/dev/sda1 / ext2 defaults 1 1
/dev/sda2 /home ext2 defaults 1 2

 
Use UUID:
	1. Get UUID for your root device. Let's assume your root file system is located in disk device /dev/sda as in the example below: 
[root at linuxhost ~]#scsi_id -g -s -u /block/sda
 
	2. Using the following command to check the ID for your root file system device with the device UUID you get from step 1. 
[root at linuxhost ~]#ls /dev/disk/by-id/<your device UUID>
 
	3. Use UUID in your system by editing /etc/fstab as in this example: 
/dev/disk/by-id/scsi-<your uuid>-part2 / ext3  defaults  1 1
 



________________________________
From: hike <mh1272 at gmail.com>
To: General Red Hat Linux discussion list <redhat-list at redhat.com>
Sent: Wednesday, July 1, 2009 11:44:44 AM
Subject: Re: How to change disk sequence on DELL R900 with LINUX

On Wed, Jul 1, 2009 at 11:21 AM, mcclnx mcc <mcclnx at yahoo.com.tw> wrote:

>
> Thank you for your answer.
>
>  I look your document and using "udev" to create "mydevXXX".  This device
> is work, but NOT what I want.
>
> The reason are:
>
> 1. what I want is my device sequence must:
>    boot and root on /dev/sda
>    swap on /dev/sdb
>
> 2. udev ONLT create a "link" from "mydevXXX" back to original.  It did NOT
> official change device name.
>  e.g.:
> lrwxrwxrwx 1 root root 3 Jul  1 11:19 mysda -> sdc
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysda1 -> sdc1
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysda2 -> sdc2
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysda3 -> sdc3
> lrwxrwxrwx 1 root root 3 Jul  1 11:19 mysdb -> sdd
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdb1 -> sdd1
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdb2 -> sdd2
> lrwxrwxrwx 1 root root 3 Jul  1 11:19 mysdc -> sde
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdc1 -> sde1
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdc2 -> sde2
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdc3 -> sde3
> lrwxrwxrwx 1 root root 3 Jul  1 11:19 mysdd -> sda
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysdd1 -> sda1
> lrwxrwxrwx 1 root root 3 Jul  1 11:19 mysde -> sdb
> lrwxrwxrwx 1 root root 4 Jul  1 11:19 mysde1 -> sdb1
>
> --- 09/6/30 (二)，Thomas Fess <dfezz1 at yahoo.com> 寫道：
>
> > 寄件者: Thomas Fess <dfezz1 at yahoo.com>
> > 主旨: Re: How to change disk sequence on DELL R900 with LINUX
> > 收件者: "General Red Hat Linux discussion list" <redhat-list at redhat.com>
> > 日期: 2009年6月30日,二,下午1:16
> > Linux defines the devices as they
> > come up or become available so depending on what your doing
> > that this, it causes an issue.  Such as san
> > disks(multipathing) and mounts or ASM in oracle or whatever,
> > you have to use another method to define a persistant name
> > to the LUN/disk etc.
> >
> > http://dims.ncsa.uiuc.edu/set/san/src/linux-mpio.pdf
> >
> >
> >
> >
> > ________________________________
> > From: mcclnx mcc <mcclnx at yahoo.com.tw>
> > To: redhat-list at redhat.com
> > Sent: Tuesday, June 30, 2009 8:51:18 AM
> > Subject: How to change disk sequence on DELL R900 with
> > LINUX
> >
> >
> > we have DELL R900 with REDHAT 5.3 in it.  This DELL R900
> > come with one integrate PERC6/I and two PERC6/E cards.
> > DELL PERC 6/I control 5 internal disks.  The original disk
> > sequence are:
> >
> > /dev/sda1 /boot
> > /dev/sda2 /
> > /dev/sdb1  swap
> > ...
> >
> > after I configured PERC 6/E disks and reboot, /dev/sda
> > change to RAID disk and original /boot and / change to
> > /dev/sde1 and /dev/sde2.
> >
> > My modprobe.conf is:
> >
> > alias scsi_hostadapter megaraid_sas
> > alias scsi_hostadapter1 ata_piix
> > alias eth0 bnx2
> > alias eth1 bnx2
> >
> > how to change sequence back?
> >
> > Thanks.
> >
> >
> >
> >
> >
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in RHEL (and I would assume Fedora), a partition can be labeled.
labels are persistent across reboots
labels can be used in the fstab file (mount table)

label can be assigned and mounted.
we use multiple disk arrays and label the partitions created by lvm.
we have no problem mounting these partitions regardless of the order that
they come up.

we were taught that the constant renaming of the disks is the result of pc
technology.
other, non-bios servers don't have this issue.
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