Erasure Coding
Erasure coding uses a set of algorithms (similar to RAID 6) to allow the recovery of missing data using a subset of original data. In theory, EC techniques uses less storage capacity than standard replication, but keeping the same durability guarantees. Erasure coding is transparent from the application perspective.
Prerequisites
In this guide we suppose you have an OpenIO SDS namespace that is ready to use, in version 7.0.0.
Configuration
To use erasure coding, you must have a storage policy with an erasure coding data security policy configured.
Here is an example of a storage policy using erasure coding:
[STORAGE_POLICY]
EC=NONE:EC_ISA_6_3
[DATA_SECURITY]
EC_ISA_6_3=ec/k=6,m=3,algo=isa_l_rs_vand,distance=1
This describes a storage policy named EC
configured with a data security policy called EC_ISA_6_3
that uses
the erasure coding backend ISA-L with the following parameters:
algo
: code of the erasure coding backend.k
: number of data chunks.m
: number of parity chunks.distance
: distance between chunks.
Name | Code | Description |
---|---|---|
ISA-L | isa_l_rs_vand |
Intel Storage Acceleration Library |
Liberasurecode | liberasurecode_rs_vand |
Software only EC Library that supports a Reed-Solomon backend. |
Jerasure | jerasure_rs_vand |
EC Library that supports Reed-Solomon backends. |
Jerasure (Cauchy) | jerasure_rs_cauchy |
EC Library that supports Cauchy backend. |
Flat XOR HD | flat_xor_hd |
Flat XOR backend. |
SHSS | shss |
NTT Lab hybrid EC backend. |