SAN booting tricks

I'd like to be able to boot from the SAN for DR purposes but I have no idea how I would take an existing boot partition...

and copy it to a SAN mounted volume. Any ideas?

A reader recently asked this question:

With STK D280 plus StoreAge SVM, I'd like to be able to boot from the SAN for DR purposes. Similarly booting via the network from SAN mounted volumes would be kind of neat. StoreAge seems to have a problem with booting from anything other than IBM servers at present (mine are Compaq DL380 and 580 servers with QLogic HBA controllers).

Even if I could boot them, I've no idea how I would take an existing boot partition and copy it to a SAN mounted volume. Any ideas? Can you point me in the direction of something that could do it for us?

Chris Poelker responded:

Yup, and here I go plugging my book again but I have a step-by-step process for booting off the SAN in chapter 10 of "Storage Area Networks for Dummies."

There are a couple of tricks you need to be aware of when doing SAN boot. First of all, you need the proper boot BIOS on your HBA, that supports it. Without the support of the boot bios on the HBA, you will never see any disks SAN. You also need to copy the correct driver to the boot partition of the disk you will be booting from in the SAN.

The best way to do this is actually install NT on the disk in the SAN. After you set up the HBA and enable the boot bios, insert the NT CD in the server and do a normal install. When you get to the section on "Install other SCSI devices" during the install process, insert a floppy with the correct driver for your HBA and it will copy it to the boot partition of the SAN based disk you chose as the C: drive. Complete the rest of the install process normally. Once finished, you can install the rest of your applications and off you go.

One issue I have seen is that using a boot partition greater than 4 GB in the SAN for a boot volume may cause the server to hang on rebooting once NT is installed. For your SAN C: drive, create a partition of 4GB or less on the LUN used for the boot disk.

Last but not least, once you have everything set up and NT is installed on the SAN disk, go into the boot bios of the Compaq server and disable the SCSI bios for all other SCSI adapters in the server with the exception of the CD-ROM drive. The server may hang on boot if this is not done since it gets confused on whether to boot from the internal disks or the primary partition in the SAN. Another way is to just yank out the internal drives. (If the internal drives are configured as a RAID set, label each drive in the correct order they were removed or you will not get your original drive back if you need it).

Note: An alternative method is to mirror the boot partition to a disk in the SAN but you will manually have to add the new driver to the SAN boot partition once the mirror is broken. Or, you can just use the GHOST utility then manually add the boot driver for the HBA you are using. I like the complete install process, since you will know everything is clean.

Windows HATES issues with access to the C: drive. Make sure you have a method of path failover and the timeout settings on the HBA are set correctly.

The cool thing about SAN boot is if your server dies, all you need to do is swap the old servers HBA into a like server and reboot. Bada bing, bada boom, all your applications are now available! I call this "poor man's clustering."

Last but not least, all bets are off if your storage or server vendor does not support booting into the storage array. Get permission to do this first or it may void your maintenance contract for that particular server or array.

For more information on booting from the SAN using Windows, click here and search for Knowledge Base article #305547. Also, my book has a lot more detail in the exact process.



This was last published in September 2003

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