

The question “How heavy is the Backblaze Cloud?” came up in a marketing meeting one Monday afternoon. “One million pounds,” someone guessed, “A hundred thousand pounds,” someone else said trying to sound sure. The truth is we had no idea. “Well, how much does a real cloud weigh?” someone else asked, and at that point we knew we had to find out more…

The Backblaze Cloud

Over the last few years, the folks at our Sacramento data center have gotten used to me asking “odd” questions. For example, how loud is the data center or what are those sticky mats on the floor. See our “A Day in the Life of a Datacenter” post if you’re curious.

With that in mind, I sent over a list of questions to our data center manager, including the following:

What does a 45-drive Backblaze Storage Pod weigh? What does a 60-drive Backblaze Storage Pod weigh? How much does an empty rack weigh?

I also asked for the weight of our networking equipment, non-storage servers, spare drives, and wiring. I did not ask about Guido, his friend Luigi, or other maintenance equipment. I just needed enough information to calculate the weight of the hardware we use to acquire and store data.

Normally the data center team in Sacramento is very responsive to my oddball requests. This time they were silent. I assumed they were busy. I tried again about a month later and this time I told them that I wanted to calculate the weight of the Backblaze Cloud. More silence. I decided to go visit one of data center team members in person with my request. After he stopped laughing, he “slacked” the data center manager, who at that moment realized I was actually serious and not playing a stupid marketing trick. I had my answers an hour later.

A 45-drive Backblaze Storage Pod weighs 140 pounds and the 60-drive Storage Pod weighs 158 pounds and so on. Based on the information provided, I calculated that the hardware we use to power the Backblaze Cloud weighs a little over 250,000 pounds, or about 113,400 kilograms.

The Backblaze Cloud weighs over 250,000 pounds

One Terabyte Per Pound

That 250,000 pounds of Backblaze Cloud hardware is used to store a little over 250 Petabytes of data. That means it takes one pound of hardware to store one terabyte of data.

Let’s take a minute and give this weight-to-data relationship the “sniff-test” by looking at the weight of a 1TB hard drive. Since we use 3 ½” drives to store data here are a few 3 ½” 1TB drives we found.

Drive Type Model Weight Seagate 1TB Desktop Internal ST1000DM003 14.1 ounces WD Red 1TB NAS Internal WD10EFRX 15.8 ounces Seagate 1TB FreeAgent GoFlex External STAC1000103 2.4 pounds WD 1TB My Book External WDBACW0010HBK-NESN 2.6 pounds

Our 1 TB per pound weight calculation fits nicely between the weight of the internal drive models and the weight of the external drive models. Also, given that 45 (or 60) internal drives share the weight of one enclosure (Storage Pod) it makes sense our weight calculation is closer to that of the internal drives. Sniff-test passed!

Comparing Clouds

Perhaps you’ve been asked by an inquisitive nine-year old, “How much does a cloud weigh?” If you answered, “its heavy” and then changed the subject perhaps we can help, although there seems to be very different answers to this supposedly simple question.

How much does a cloud weigh? a. 216,000 pounds (NPR) b. 1.1 million pounds (mental_floss) c. 8.8 million pounds (Zidbits) d. All of the above.

Technically a cloud has little or no weight, otherwise you’d be crushed to death the next time the fog rolled in. The question should be, “How much is the mass of a cloud?”, but most nine-year old children haven’t learned about mass yet.

Back to the question at hand, the correct answer is “d.” How can all three be correct? Simple, they used different types of clouds, different sized clouds, or both. For example, a white fluffy cumulus cloud holds about 1/2 gram of water per cubic meter, while a cumulonimbus cloud can hold up to 5 grams of water per cubic meter – 10 times as much in the same volume.

Based on what we’ve learned so far, we can actually determine how big a fluffy cumulus cloud would have to be to have the same weight (250,000 pounds/ 113,400 kg) as the Backblaze Cloud:

Cumulus cloud weight = 0.5 grams per cubic meter

Backblaze Cloud weight = 113,400 Kilograms or 113,400,000 grams

Cumulus cloud volume = 113,400,000 grams / (0.5 grams * 1 cubic meter)

Cumulus cloud volume = 226,800,000 cubic meters

Based on this, if we had a cumulus cloud that was 16.5 feet (5 meters) high, about the height of a data center, it would cover an area of 45,360,000 square meters. That’s 45.36 square kilometers or 17.51 square miles.

Comparing clouds, the Backblaze Cloud is equal to a fluffy white cumulus cloud that is around 16.5 feet high and 17.5 miles square. Thank goodness our data center team uses their space a little more efficiently.



Afterthoughts

If nothing else, the next time an inquisitive nine-year old asks, “How much does a cloud weigh?” you’ll have an answer, or two, or three. Of course the next question could be “Why don’t clouds fall from the sky?” and you’ll have to talk about weight and mass and volume and thermal updrafts and all that, or you can just change the subject…

The one thing I do know is that no two clouds are alike. That’s true for real clouds or data storage clouds. That means our cloudy math could be perfect for sunny days in Hawaii and completely wrong for rainy days in Brazil, or vice-versa. If you can shed some light on the weight of a cloud – the real kind or the data storage kind – let us know in the comments.