What is the largest external hard drive or RAID supported by Yosemite and El Capitan?

FYI............2 UPDATES since I posted this question:

1. Drobo has UPDATED their FIRMWARE to now allow for 64 TB "Beyond RAID" Drobos. So, their original 16 TB limit has now been superseded by their new Limit of 64 TB. Also, note that, when using a Drobo, Apple's Mac OS does not properly show the "Drive Space" and the "Free Space," if the Drobo exceeds 16 TB in size; but, the Drobo DashBoard Application does show the Correct Numbers. For example, my Drobo 5D contains 5, 8 TB Drives, for a Total Beyond RAID Size of 40 TB (in theory, since most of us should know, by now, that the ACTUAL SIZE IS SLIGHTLY LESS THAN THE THEORETICAL SIZE). The ACTUAL SIZE AVAILABLE FOR USE IS ONLY 28.9 TB. Thus, 40 - 28.9 = 11.1 TB gets used-up for the Beyond RAID PROTECTION and the difference between ACTUAL SPACE versus THEORETICAL SPACE. THIS IS NORMAL because any RAID 5 Device always uses about 1 Hard Drive Size for its Protection. So, knowing this fact, the DeskTop Icon should be showing the Drive Space as 28.9 TB and the Free Space as whatever is not yet used. However, instead, the Mac OS shows the Drive Space as 70.37 TB and the Free Space as 68.37 TB, which are both incorrect. Although I would love it if the Mac OS was magically increasing my Hard Drive Space, in fact, both numbers are false. Drobo knows this and Apple does not, from my discussions with both. So, between the two companies, I hope this problem can be fixed.

2. After many hours on the telephone with Apple Support, going through no less than 6 people, including 2 Senior Advisors, NONE OF THEM COULD ANSWER MY QUESTION ABOUT WHAT IS THE MAXIMUM ALLOWD HARD DRIVE OR RAID SPACE ALLOWED BY Yosemite and El Capitan. To me, THIS IMPORTANT TECHNICAL FACT SHOULD SIMPLY BE LISTED IN THE OS SPECIFICATION, that is easy and quick to read on the Support Site. But, Apple being the new bureaucracy that they are, I do not see this happening, anytime soon. So, just be aware that, for now, THERE IS NO LIMIT ON SIZE, as one Apple Advisor said; but, could not confirm in writing; and, THERE IS AN INCORRECT DISPLAY OF SIZE AND FREE SPACE, if your Drive exceeds an unknown 16+ TB in size. Note that I do have 3 other RAIDs that are correctly showing-up as 9 TB, 12 TB and 18 TB in size; but, I do not know at which point SIZE DOES MATTER so that the OS displays it incorrectly, except for my 40 TB Drobo. So, bottom line, somewhere in between 18 TB and 40 TB is where it goes false, in its display of sizes.

FYI............2 UPDATES since I posted this question:

1. Drobo has UPDATED their FIRMWARE to now allow for 64 TB "Beyond RAID" Drobos. So, their original 16 TB limit has now been superseded by their new Limit of 64 TB. Also, note that, when using a Drobo, Apple's Mac OS does not properly show the "Drive Space" and the "Free Space," if the Drobo exceeds 16 TB in size; but, the Drobo DashBoard Application does show the Correct Numbers. For example, my Drobo 5D contains 5, 8 TB Drives, for a Total Beyond RAID Size of 40 TB (in theory, since most of us should know, by now, that the ACTUAL SIZE IS SLIGHTLY LESS THAN THE THEORETICAL SIZE). The ACTUAL SIZE AVAILABLE FOR USE IS ONLY 28.9 TB. Thus, 40 - 28.9 = 11.1 TB gets used-up for the Beyond RAID PROTECTION and the difference between ACTUAL SPACE versus THEORETICAL SPACE. THIS IS NORMAL because any RAID 5 Device always uses about 1 Hard Drive Size for its Protection. So, knowing this fact, the DeskTop Icon should be showing the Drive Space as 28.9 TB and the Free Space as whatever is not yet used. However, instead, the Mac OS shows the Drive Space as 70.37 TB and the Free Space as 68.37 TB, which are both incorrect. Although I would love it if the Mac OS was magically increasing my Hard Drive Space, in fact, both numbers are false. Drobo knows this and Apple does not, from my discussions with both. So, between the two companies, I hope this problem can be fixed.

2. After many hours on the telephone with Apple Support, going through no less than 6 people, including 2 Senior Advisors, NONE OF THEM COULD ANSWER MY QUESTION ABOUT WHAT IS THE MAXIMUM ALLOWD HARD DRIVE OR RAID SPACE ALLOWED BY Yosemite and El Capitan. To me, THIS IMPORTANT TECHNICAL FACT SHOULD SIMPLY BE LISTED IN THE OS SPECIFICATION, that is easy and quick to read on the Support Site. But, Apple being the new bureaucracy that they are, I do not see this happening, anytime soon. So, just be aware that, for now, THERE IS NO LIMIT ON SIZE, as one Apple Advisor said; but, could not confirm in writing; and, THERE IS AN INCORRECT DISPLAY OF SIZE AND FREE SPACE, if your Drive exceeds an unknown 16+ TB in size. Note that I do have 3 other RAIDs that are correctly showing-up as 9 TB, 12 TB and 18 TB in size; but, I do not know at which point SIZE DOES MATTER so that the OS displays it incorrectly, except for my 40 TB Drobo. So, bottom line, somewhere in between 16 to 18 TB and 40 TB is where it goes false, in its display of sizes. Also, note that this might only be an issue with External Drobo BeyondRAID Drives, as well. I have no way of knowing this because I have no other RAID Drive that is this large, to compare it with.