There are two different ways that you can run iSCSI from your PC server embedded and installable. Let's take a look at the difference. VMware uses the term embedded. When you have iSCSI baked into flash memory on the motherboard of your PC server. Dell, for example, is a big fan of providing servers with iSCSI right on the motherboard. The idea there is you can go into the machine's bios and you can configure it so that the esxi host boots iscsi from flash memory right off the motherboard right after the power on self-test completes. Now as far as the iSCSI host configuration that can reside either locally on the same flash storage media or it can be retrieved from the network. For high end VMware installs, VMware provides a service called auto deploy. Auto deploy allows your esxi host to boot from the network. So auto deploy not only provides the operating system from the network, but it provides the exact host configuration from the network using a service called Host profiles. Now most of us are going to be doing ESXi Installable and that's the actual focus of the remainder of this chapter, is to install ESXi on the local storage volumes. Those storage volumes can be disks or they can be SSDs. Now, regardless of whether they are spinning disks or SSDs, you can organize them into raid arrays using a locally supported array controller and VMware supports raid controllers from LSI Logic Adaptec, HP, Smart array controller, Dell's Poweredge raid controller and many others. Or you can just hang them off of Sata ports, in which case what you have is something called a just or a jbod, which means just a bunch of disks. It means physical disks or SSDs with no raid structures imposed on them. Now you can actually install iSCSI onto a USB thumb drive, a flash memory thumb drive or or an SD card and you can boot from that. So the advantage of flash boots is that you don't have to buy a raid controller, you don't have to buy a local storage volume other than the flash memory card or SD card. You simply take iSCSI using procedures VMware provides and copy it to a USB key and then configure the ESXi host to boot off the OS image on that USB key. And where I just said USB key, you could also do the same thing with an SD card. The neat thing about this is that flash memory is relatively easy to duplicate. You can duplicate it on any computer at very low cost, so you can have some spare flash media devices around in case your flash memory device fails. And most modern PC servers have internal USB ports or SD card slots. So you can actually plug the flash memory device into an internal port. And the advantage of having it on an internal port is that. It's fully enclosed in the PC server. It can't be bumped, it can't be removed. So your server just continues to function.
