sherpa: All content tagged as sherpa in NoSQL databases and polyglot persistence
Information about Yahoo! PNUTS/Sherpa is so rare. Except the original PNUTS architecture paper (PDF) and the Sherpa: Cloud Computing of the Third Kind slides (PDF), it’s difficult to find something else. But in September, the Yahoo! Developer blog posted an update about Sherpa.
- 500+ Sherpa tables
- 50,000+ Sherpa tablets(shards) in operation
- tablets can be copied, moved, or split dynamically
- multi-data center
- multi-tenant: it must support different ranges of read/write ratios
- 75000 requests per second
- supports heterogeneous servers
- some are SSD exclusively
- Sherpa users have access to monitoring tools to examine their app latency and throughput SLA. This implies each application could negotiate different SLAs with the infrastructure team.
- Sherpa default storage engine is MySQL/InnoDB
- storage access have been abstracted
- Yahoo! tested BDB, BDB-Java, and Log-Structured Merge (LSM) Tree developed by Yahoo Labs backends
- Sherpa relies on a reliable messaging system
- can guarantee reliable in-colo and cross-colo transactions
Selective Record Replication
- previous versions supported Table-level replication
- new version support Record-level replication
- designed for efficiency (minimize costs of transfer and storage) and legality (ensure copyright regulations, other legal concerns)
- replication locations are declarative/static
- Sherpa maintains a ‘stub’ of the record in locations that do not have a full copy
- the stub is updated only when a record is created, deleted, or when replication rules change
- the stub is used for routing requests
- Support for full table backups has been added
- Point-in-time recovery planned
- Also planned full, cross-colo, and automatic table restoration
Task Manager using Sherpa Tables for Task State
- Sherpa has added a general workflow manager to execute long-running tasks
- It is used for backup and restore operations
The complete post can be read here.
Considering Yahoo! has always been a big proponent of open source projects, it is a pitty that we don’t have the chance to hear more often and more details about PNUTS/Sherpa.
Original title and link: Yahoo! Sherpa: Status and Advances ( ©myNoSQL)
From ☞ Amandeep Khurana a nice matrix comparing characteristics of Cassandra, HBase and PNUTS:
Recently, in a course that I’m taking at UC Santa Cruz, I got a chance to present the PNUTS paper and compare the system with Bigtable and Dynamo.
The Cassandra, HBase, and PNUTS matrix includes details about:
- data model
- consistency model
- ACID semantics
- fault tolerance
You should also check Cassandra and HBase Compared