A really cool technique that’s commonly used in object storage such as S3 to improve durability is called Erasure Coding. Let’s take a look at how it works.
Erasure coding deals with data durability differently from replication. It chunks data into smaller pieces (placed on different servers) and creates parities for redundancy. In the event of failures, we can use chunk data and parities to reconstruct the data. Let’s take a look at a concrete example (4 + 2 erasure coding) as shown in Figure 1.
How much extra space does erasure coding need? For every two chunks of data, we need one parity block, so the storage overhead is 50% (Figure 2). While in 3-copy replication, the storage overhead is 200% (Figure 2).
Does erasure coding increase data durability? Let’s assume a node has a 0.81% annual failure rate. According to the calculation done by Backblaze, erasure coding can achieve 11 nines durability vs 3-copy replication can achieve 6 nines durability.
A really cool technique that’s commonly used in object storage such as S3 to improve durability is called Erasure Coding. Let’s take a look at how it works.
Erasure coding deals with data durability differently from replication. It chunks data into smaller pieces (placed on different servers) and creates parities for redundancy. In the event of failures, we can use chunk data and parities to reconstruct the data. Let’s take a look at a concrete example (4 + 2 erasure coding) as shown in Figure 1.
How much extra space does erasure coding need? For every two chunks of data, we need one parity block, so the storage overhead is 50% (Figure 2). While in 3-copy replication, the storage overhead is 200% (Figure 2).
Does erasure coding increase data durability? Let’s assume a node has a 0.81% annual failure rate. According to the calculation done by Backblaze, erasure coding can achieve 11 nines durability vs 3-copy replication can achieve 6 nines durability.