SAN Attached Hosts

Managing SAN storage on an open systems platform is a little diffiernt compared with managing direct attached or internal storage. Typically direct attached storage is not added to a running server however with a storage area network an administrator working hundreds of miles away can make new storage available to a host attached to the storage network. The following techniques may be helpful to OS admins bringing the storage on line.

  • Solaris - Often with SAN attached Solaris hosts it is advisable to configure a few extra luns in /kernel/drv/sd.conf when the host is first attached. This makes it possible to add additional luns without need for a reboot. The downside is that when a reboot is needed the boot process will be a bit slower because the host will probe for the configured luns which haven't been added yet. In some cases with the older arrays this may not really be practical because the host lun number assignment may not be very predictable. Since you can't predict which lun you'll get next you may be tempted to configure 255 luns in advance. This will add very noticable boot time. Once the sd.conf file is configured and the host has been rebooted any newly presented luns can be made available by running the "devfsadm -C" command. After running devfsadm the new disks will show up in "format". The first time you select a newly presented lun in format you will have to label the disk. Note - Veritas VM will ignore unlabeled disks. The procedure is a bit different if you use Sun branded QLogic HBA's. With these cards, "cfgadm -c configure c#" is all that is required to bring online newly added luns. No additional sd.conf entries are required. Also with the Sun branded QLogic cards Sun's mpxio DMP software may be configured as an alternative to Secure Path or VxVM DMP etc.

  • HP-UX - HP-UX is a little better when it comes to dynamically adding hardware. I hate to admit that because I've always loved Solaris and Sun hardware. With HP-UX all that is usually required after adding new luns from a SAN is "ioscan -fnC disk" followed by "insf -e". HP-UX also provides a nice utility for their Tachyon HBAs called fcmsutil which can be used to get HBA WWN's and confirm connectivity to remote array ports.

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