1. Gowtham Rajappan

2. HDFS – Hadoop Distributed File System modeled on Google GFS.
Hadoop MapReduce – Similar to Google MapReduce
Hbase – Similar to Google Bigtable 2

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5. Master: hadoop01.cselabs.umn.edu
Slaves: hadoop02 – hadoop05.cselabs.umn.edu
You will require cselabs account to access this cluster. You can login to any of these machines from any cs/cselabs machine. 5

6. Data is divided into various tables
Table is composed of columns, columns are grouped into column- families 6

7. Persistence and data availability
Partitioning
A table is horizontally partitioned into regions, each region is composed of sequential range of keys
Each region is managed by a RegionServer, a single RegionServer may hold multiple regions
Persistence and data availability
HBase stores its data in HDFS, it doesn't replicate RegionServers and relies on HDFS replication for data availability.
Region data is cached in-memory
Updates and reads are served from in-memory cache (MemStore)
MemStore is flushed periodically to HDFS
Write Ahead Log (stored in HDFS) is used for durability of updates 7

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9. HBase shell provides interactive commands for manipulating database
Create/delete tables
Insert/update/read from tables
Manage regions 9

10. Hbase provides single row atomic operations
CheckAndPut – Similar to test-and-set
CheckAndDelete
All row operations are atomic no matter how many columns are involved.
Hbase also provides row level exclusive locks
You can use these locks to implement single row level transactions 10

11. Each update to a row creates a new version, for the specified column.
HBase stores multiple versions of a column in a row. Each version is identified by a integer timestamp
By default system time is used as version timestamps. However user can specify a logical timestamp for versioning
Each update to a row creates a new version, for the specified column.
A version can be accessed or deleted using its timestamp. HBase allows to obtain list of all the versions. 11

12. Hadoop Home - http://hadoop.apache.org/
Hbase -
API 12