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© 2002 IBM Corporation
IBM Haifa Research Laboratory
IBM Systems and Storage Seminar | 24/11/2003
Improving Database Functionality and Performance Using an Object Store Architecture
Gary Valentin Noam Rinetzky Michael Factor
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation2
Research Goals
§Potential benefits of Object Stores (ObS) to Data Base Managers (DBM)
§Effects of ObS technology on DBM design
§Making ObS more attractive for DBM√
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation3
Outline
§Background– Database managers storage model
– Object Store
§DBM / ObS§Expected benefits§Prototype Implementation §Related work§Conclusions
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation4
Database Managers
Programs that manage data§ Insert, delete, update, query, etc. via SQL§Advanced services
– Backup, transactional access, …
§Responsible for storing the data– Store data in tables and indexes
– Use various data structures
– B+Trees, heaps, …– Data layout is invisible to end-user
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation5
DBM Storage ModelsFile system
managed data§ DBM: places each table
and index in a separate file§ File system: manages
the storage
DBM managed data
§ DBM works with raw partitions§ Takes responsibility
for storage management
ObSmanaged data
DBM
Block Device
DBM
Object Store
DBM
Block Device
File System
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation6
What is an Object Store?
What is a block device?§ Abstraction: array of unrelated
blocks§ Access: based on block
number
What is an object store?§ Abstraction: collection of
storage objects§ Access: object id, range
0x1000x000
0x3000x200
0x4000x400
…
O2 O4
O1O3
O5
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation7
What is an Object Store?
ObS interface§ Create / delete object§ Read / write byte range in an
object§ Set / Get object attributes
O2 O4
O1O3
O5
ObS is responsible for§ Managing object meta data
– Offset à data
– Attributes§ Free space management
ObS provides a higher level of abstraction
What is an object store?§ Abstraction: collection of
storage objects§ Access: object id, range
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation8
DBM ObS Storage Model
§ Each table / index is mapped to a different storage object§ By design, similar to the
FS-MD modelHowever, storage management is done by the ObS and not by the file system
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation9
Expected Benefits
Performance§Code path
reduction § Improved caching §Atomic writes§Advanced Search
Functions
Functionality§Quality of Service §Object point in time
copy§Object encryption§Object compression
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation10
Performance Boosting via Code Path Reduction§ ObS-MD minimizes the
storage management code path on the DBM host
FS-MD: FS-layer overhead
DBM-MD: DBM Storage management overhead
ObS-MD: Storage management overhead moved to storage server
§ Conjecture: moving work from DBM host to the storage server is beneficial
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation11
Performance Boosting via Code Path Reduction§ ObS-MD minimizes the
storage management code path on the DBM host
FS-MD: FS-layer overhead
DBM-MD: DBM Storage management overhead
ObS-MD: Storage management overhead moved to storage server
§ Conjecture: moving work from DBM host to the storage server is beneficial
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation12
Object Compression
Pros§ Transparent to DBM§ Does not use DBM host
CPU cycles§ Efficient compression
– large blocks
Cons§ Complicates object
updates§ Does not save network
bandwidth
ObS can provide lossless object compression
The DBM may choose to compress only suitable objects
e.g. rarely modified large text objects
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation13
Prototype Implementation
§Modified DB2 Universal database V8.1 to use a native ObS interface§Changed components
– Data cache
– Agents
– Prefetchers
– Page cleaners
§ Internal object store prototype
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation14
Object Caching
§ Prototyped the ability to specify which objects to cache§ Scanned tables:
– 60MB size
– 1M records
Conclusions• Performance gained by caching object in the ObS cache approaches optimal• Changing the ObS caching policies, i.e., according to QoS considerations can influence the DBM overall performance
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation15
Related Work
§Object Stores:NASD [G. Gibson et al., 1997]
ObS Security [Gobioff 1999, A. Azagury et al., 2002]
T10 OSD standard §DBM & Storage
My cache or yours? [T. M. Wong and J. Wilkes 2002]
Lachesis [B. Schindler et al. 2003]
Active storage [E. Reidel et al. 1998]
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation16
Conclusions
Object store managed data model
§ An attractive alternative to current storage models§ Provides many benefits
– Performance: code path reduction, caching, advanced search function, atomic writes
– Functional: QoS, point in time copy, object encryption, object compression
§ Benefits originate from – ObS higher level of abstraction
– DBM deep understanding of the objects it maintains
§ Fits well with current DBM design
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation17
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© 2002 IBM Corporation
IBM Haifa Research Laboratory
IBM Systems and Storage Seminar | 24/11/2003
Coffee time
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation19
Advanced Search Functions
§A search of a string in a not-indexed column leads the DBM to read an entire table§An advanced search function would allow
the DB to send the string to the OBS and get back the offsets in an object in which a match was found§Save network bandwidth and CPU cycles
from DBM host
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IBM Haifa Research Laboratory
Improving Database Functionality and Performance Using an Object Store Architecture © 2002 IBM Corporation20
Atomic Writes
§ SCSI Block devices guarantee atomic writes at sector granularity§ DBM manages tables with
different page sizes– e.g., 4K, 8K, 16K, 32K
§ Pages has to be written atomically§ Partial page is an unrecoverable
situation
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4K page = 8 sectors
Can dofrom log
Can undo from log
ObS solution: set atomic write length as an object property
Restore from backup
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