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Boot from SAN and regular Boot

Boot from SAN and regular Boot

Any Expert to explain the difference between booting from SAN and regular boot.

Thank you
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Avatar of Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
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You can boot a diskless server from a SAN. You have to configure a LUN to boot from and configure the HBA to use it. For VMware it's not really worth the trouble to configure since booting from SD card is simpler, may be worth doing for a large environment or a remote one though as it's a bit quicker to swap a spare server in as a replacement for a failed host by setting it to boot from the previous host's boot LUN than taking one apart to get the SD card out.
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ASKER

you mean If you have a Blade Chassis then the blades do not have local storage. So the Chassis HBA adapter will be configured with the SAN to boot from the SAN ?
Correct, some blades are diskless.

So the Chassis HBA adapter will be configured with the SAN to boot from the SAN ?

Correct.

It was a popular solution many years ago, (16 years) but flash, nVME, M.2 SATA, MDOM have now all become popular mechanisms of local boot.

for many years Windows OS because of many reads and writes at BOOT had issues with USB and Flash, but that not much of an issue now with flash-based nVME devices.
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ASKER

Nowadays, for the Blade chassis , does each blade have local disk ?
They can be purchased with or without local disks.

Available as options.
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ASKER

Thank you Guys!!
The original question was "explain the difference between booting from SAN and regular boot."

Well the simple answer is there is NO difference!

The PC BIOS boots off the disks it can see,

Local (directly) attached disks are made visible by the Storage HBA (maybe built in) so SATA & SAS disk look like SCSI attached disks to the BIOS, guess what SAN presented LUNs look like SCSI disks too!
So the BIOS sees whatever devices are presented to it, a SAN HBA can present what looks like a locally attached SCSI disk to the BIOS - hence the BIOS can boot off it, like any other "locally" attached disk

The trick is configuring the HBA/NIC to present the SAN device to the BIOS, once that is done, there is no difference between a locally attached disk and a SAN attached LUN

By the way we were doing this back in the last century! I built a Proof of concept system for a customer in the UK in the late 90's,  that they then rolled out to multiple locations across the UK