{"id":74771,"date":"2017-03-10T09:30:54","date_gmt":"2017-03-10T17:30:54","guid":{"rendered":"https:\/\/www.backblaze.com\/blog\/?p=74771"},"modified":"2025-12-11T14:15:32","modified_gmt":"2025-12-11T22:15:32","slug":"the-clouds-software-a-look-inside-backblaze","status":"publish","type":"post","link":"https:\/\/www.backblaze.com\/blog\/the-clouds-software-a-look-inside-backblaze\/","title":{"rendered":"The Cloud’s Software: A Look Inside Backblaze"},"content":{"rendered":"

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When most of us think about “the cloud,” we have an abstract idea that it’s computers in a data center somewhere\u2014racks of blinking lights and lots of loud fans. There’s truth to that. Have a look inside our data center<\/a> to get an idea. But besides the impressive hardware\u2014and the skilled techs needed to keep it running\u2014there’s software involved. Let’s take a look at a few of the software tools that keep our operation working.<\/p>\n

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Our data center is populated with Storage Pods<\/a>, the servers that hold the data you entrust to us if you’re a Backblaze customer or you use Backblaze B2 Cloud Storage<\/a>. Inside each Storage Pod are dozens of 3.5inch spinning hard disk drives\u2014the same kind you’ll find inside a desktop PC. Storage Pods are mounted on racks inside the data center. Those Storage Pods work together in Vaults.<\/p>\n

Vault Software<\/h2>\n

The Vault software<\/a> that keeps those Storage Pods humming is one the backbones of our operation. It’s what makes it possible for us to scale our services to meet your needs with durability, scalability, and fast performance.<\/p>\n

The Vault software distributes data across 20 different Storage Pods, with the data spread evenly across all 20 Pods. Drives in the same position inside each Storage Pod are grouped together in software in what we call a Tome. When a file gets uploaded to Backblaze, it’s split into pieces we call Shards and distributed across all 20 drives.<\/p>\n

Each file is stored as 20 shards: 17 data shards and three parity shards. As the name implies, the data shards comprise the information in the files you upload to Backblaze. Parity shards add redundancy so that a file can be completely restored from a Vault even if some of the pieces are not available.<\/p>\n

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Because those shards are distributed across 20 Storage Pods in 20 cabinets, a Storage Pod<\/a> can go down and the Vault will still operate unimpeded. An entire cabinet can lose power and the Vault will still work fine.<\/p>\n

Files can be written to the Vault even if a Storage Pod is down with two parity shards to protect the data. Even in the extreme\u2014and unlikely\u2014case where three Storage Pods in a Vault are offline, the files in the vault are still<\/em> available because they can be reconstructed from the 17 available pieces.<\/p>\n

Reed-Solomon Erasure Coding<\/h2>\n

Erasure coding makes it possible to rebuild a data file even if parts of the original are lost. Having effective erasure coding is vital in a distributed environment like a Backblaze Vault. It helps us keep your data safe even when the hardware that the data is stored on needs to be serviced.<\/p>\n

We use Reed-Solomon erasure encoding. It’s a proven technique used in Linux RAID systems, by Microsoft in its Azure cloud storage, and by Facebook, too. The Backblaze Vault Architecture is calculated at 99.999999999% annual durability<\/a> thanks in part to our Reed-Solomon erasure coding implementation.<\/p>\n

Here’s our own Brian Beach with an explanation of how Reed-Solomon<\/a> encoding works:<\/p>\n