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The first stumbling block for booting from the SAN is not technical, but political. Larger IT organizations are creating storage administration groups that are responsible for the provisioning, securing and protection of application storage. However, the system administrator assigned to the business unit that owns the application server usually administers the operating system disk locally and independently of the storage group.
From the system administrator's point of view, the boot disks are the brains of the computer, and they don't want some fallible network between the physical server and its brains. This concern was both real and valid in light of the initial complexity of SANs. However, times have changed. Fibre Channel (FC)-based SANs are much more stable than they have been in the past. Interoperability between hardware and software offerings has increased, drivers are stabilizing and there are more quality gigabit interface converters (GBICs) and HBAs available on the market today. All of this lends itself to a more quality connection between a server and its boot disks on the SAN. And while there have been some isolated successes when booting from an IP SAN, FC's head start is obvious in this solution space.
What I'm hearing from the storage administrators in the field is that from a management point of view, it only makes sense to boot their servers from the SAN.
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Lack of standards
One thing is true: If the opportunity to boot from the SAN is proven useful, operational standards must be defined and abided by without exception. And trying to get different system administrators with different preferences and habits to agree on standardization is difficult.
However, I've seen it done with organizations that are serious about doing what is best for the company as a whole and not necessarily driven by individual desires.
One milestone on the path to booting from the SAN is for cooperating groups to agree to have the fewest number of boot images for their production and development servers. If a particular group of application servers need additional modifications above the standard install, then that request can be serviced with a post-execution script after the install has completed. Simplicity should be the goal here. In the end, you want to be able to do as I described above--recover a JumpStart-like server with standard Unix utilities and start snapping off boot disks.
In order to provide the same minimum level of service across business units, standardization from the HBA to the storage port must be guaranteed. This helps to address the system administrators concern about the quality of the connection between the server and its boot disks. That means that the same hardware, driver and firmware revisions supporting the boot disk connections for one group of application servers must be present in all others. If individual system administrators' personal preferences for operating systems, HBAs or other configuration components are allowed, than no real standardization will be possible. On the other hand, standardizing on quality physical connections, stable device drivers and generally agreed upon configurations usually brings goodness to all corners of the organization, including the serving of boot images from the SAN.
This was first published in December 2003