Your current path is:
The Apple Mac mini 'Core i7' 2.0 Server (Mid-2011) features a 32-nm 'Sandy Bridge' Quad Core 2.0 GHz Intel 'Core i7' (2635QM) processor with four independent processor 'cores' on a single chip, a 6 MB shared level 3 cache, 4 GB of 1333 MHz DDR3 SDRAM (PC3-10600) memory, dual 500 GB hard drives, and Intel HD Graphics 3000 with 384 MB of memory.
Upgrading to El Capitan
My friend's mid 2011 iMac (2.5 i5 with 16GB of ram) is still on 10.8. I know that I could install 10.13 on it, but is it optimal? Sometimes newer OSes are slower on older machines. So, what's the best OS for such an iMac? (My friend doesn't need the new bells and whistles, nor the incredible emojis of the latest OSes.) Thanks Loa. Oct 31, 2019 Use the Mac operating system that came with your Mac, or a compatible newer version If you try to use an incompatible macOS, your Mac might not finish starting up, or it might behave unexpectedly. If you try to start up your Mac from a hard disk, network volume, or Time Machine backup that contains an incompatible version or build of macOS.
You can upgrade to El Capitan from Lion or directly from Snow Leopard. El Capitan can be downloaded from the Mac App Store for FREE.
Upgrading to El Capitan
To upgrade to El Capitan you must have Snow Leopard 10.6.8 or Lion installed. Download El Capitan from the App Store. Sign in using your Apple ID. El Capitan is free. The file is quite large, over 5 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.
Macs that can be upgraded to OS X El Capitan
1. iMac (Mid 2007 or newer) - Model Identifier 7,1 or later
2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) - Model Identifier 5,1 or later
3. MacBook Pro (Mid/Late 2007 or newer) - Model Identifier 3,1 or later
4. MacBook Air (Late 2008 or newer) - Model Identifier 2,1 or later
5. Mac mini (Early 2009 or newer) - Model Identifier 3,1 or later
6. Mac Pro (Early 2008 or newer) - Model Identifier 3,1 or later
7. Xserve (Early 2009) - Model Identifier 3,1 or later
To find the model identifier open System Profiler in the Utilities folder. It's displayed in the panel on the right.
Are my applications compatible?
See App Compatibility Table - RoaringApps
You can upgrade directly from where you are now.