Installing Linux /Storage area network

[Nigel Wade]

Rick Stevens wrote:
> On Mon, 2005-11-21 at 13:24 -0500, Nair, Murlidharan T wrote:
> 
>>I am trying to setup my server from scratch. I have to install the OS
>>and set up SAN as database store. I also need to configure it. I have 4
>>drives so I am thinking of configuring it as 4 drive -RAID 5 without the
>>hot-spare. I have never done this before. Do you have any step by step
>>procedure on how to do this? Thanks ../Murli
> 
> 
> So you wish to install the OS on the normal IDE or SCSI (or SATA) drives
> in the machine and reserve the SAN for database?  Ok, that's fine.
> 
> As far as the SAN is concerned, I always try to configure things with a
> hot spare if at all possible.  If you need the space, then a 4-drive
> RAID5 is fine.  If you can add a hot spare later, then that's even
> better.
> 
> Each LUN on the SAN will appear as a SCSI disk (/dev/sda, /dev/sdb,
> depending on what other stuff you have).  Configure your database to
> use raw devices or set up partitions on those disks as you see fit.
> 
> Note, however, that multi-LUN setups will have problems as the default
> kernels from Red Hat only look at the first LUN.  Just why they do that
> is beyond me for an "enterprise" kernel (probing multiple LUNs is pretty
> innocuous), but that's what they do.  To get around that, you need to
> rebuild the kernel with "CONFIG_SCSI_MULTI_LUN=y" set and boot that
> kernel.
> 

With the RHEL AS4 setup I have, all I had to do was set an option in 
/etc/modprobe.conf (options scsi_mod max_luns=32). I have multiple LUNs on an 
external RAID:

/dev/sg12: scsi7 channel=0 id=0 lun=0
/dev/sg13: scsi7 channel=0 id=0 lun=1
/dev/sg14: scsi7 channel=0 id=0 lun=2
/dev/sg15: scsi7 channel=0 id=0 lun=3
/dev/sg16: scsi7 channel=0 id=0 lun=4
/dev/sg17: scsi7 channel=0 id=0 lun=5
/dev/sg18: scsi7 channel=0 id=0 lun=6
/dev/sg19: scsi7 channel=0 id=0 lun=7
/dev/sg20: scsi7 channel=0 id=0 lun=8
/dev/sg21: scsi7 channel=0 id=0 lun=9
/dev/sg22: scsi7 channel=0 id=0 lun=10
/dev/sg23: scsi7 channel=0 id=0 lun=11
/dev/sg24: scsi7 channel=0 id=0 lun=12

The kernel is as supplied by RH (2.6.9 x86_64).


-- 
Nigel Wade, System Administrator, Space Plasma Physics Group,
             University of Leicester, Leicester, LE1 7RH, UK
E-mail :    nmw at ion.le.ac.uk
Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555