WalB: Real-time and Incremental Backup System for Block Devices

WalB is an open-source backup system that consists of block devices, called WalB devices, and userland utilities, called WalB tools. A WalB device records write-I/Os. WalB tools extracts them to creat …

WalB is an open-source backup system that consists of block devices, called WalB devices, and userland utilities, called WalB tools. A WalB device records write-I/Os. WalB tools extracts them to create restorable snapshots in an incremental manner. Compared with dm-snap and dm-thin, WalB is designed to achieve small I/O latency overhead and short backup time. We conducted an experiment to take an incremental backup of a volume under random write workload. The result confirms those advantages of WalB. Cybozu cloud platform, which has 500TB volumes and processes 25TB write-I/Os per day, is required to achieve (1) stable workload performance without I/O spikes which may affect application user experience and (2) short backup interval specified in our service level objective. WalB satisfies the requirements, while dm-snap is not enough to and dm-thin is not expected to.