1) Upgrade the server (MCS7845-H2 a.k.a. HP DL380 G5) BIOS and firmware.
2) Upgrade VMware ESXi 5.0 to 5.5U2.
3) Upgrade UC 7.0 to UC 10.5.
It turned out that upgrading a system that's been collecting dust is VERY different from upgrading a system that's been up and running.
First of all, the system won't boot. Just gives me long beeps and the "Internal Health" and "External Health" LEDs are both red. Pull all memory chips out and resit them solves the problem.
Then iLO configuration seems to be lost due low power level of the system battery. I can't log into iLO at all (the 'default password' is system specific with unique numbers). Set the "System Maintenance Switch" S1 to "On" bypasses the iLO password.
When trying to upgrade to ESXi 5.5 U2, I got the following error:
I know what it is. But how could this be not enabled while I have ESXi 5.0 on it before? Maybe it's also due to the motherboard battery? Anyway, go into BIOS and enable the "No-Execute Memory Protection".
In order to use the "Web Client", you'll have to set up a vCenter server. Also, to view VM console from web browser, you'll need to install a plug-in, which doesn't work with Internet Explorer (as of today).
When installing UCM 10.5, it took extremely long (> 10 hours). Further investigation revealed that the array controller battery died. Without battery, the array controller will disable cache, which makes it very, very slow on a RAID5 (slower than my laptop).
I have multiple options:
Option 1: Order one from eBay. It's not expensive (~ $12 a piece). The problem is - this kind of batteries are obsolete. Thus the ones on eBay are all used ones, which were manufactured a couple years ago. Who knows how long they'll last.
Neither of the above options is quick enough for me. Thus I choose...
Option 3: "Enable Cache Without Battery".
To do this, you'll need ACU (Array Configuration Utility). You can do it with the ROM-based interface (BIOS).
With VMware ESXi, the easiest way is to download the "offline ACU", which is a CD you boot from. Then configure the array controller from there.
For a RAID, it's the write operation that takes more time. Thus you want to make sure the write cache is not zero.
Last but not the least, download HP SPP DVD to update all firmwares and BIOS.
P.S. DHCP doesn't work on UCM 10.5 in case you want to use UCM as a DHCP server. https://supportforums.cisco.com/discussion/12224526/cucm-105-dhcp-not-working