Docadmin at 21:00, 22 January 2010

2010-01-22T21:00:58Z

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	'''''Note:''''' The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.		'''''Note:''''' ''The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.''

	== Summary ==		== Summary ==

Docadmin: Protected "Architecture - Commit on Share" ([edit=sysop] (indefinite) [move=sysop] (indefinite))

2010-01-21T19:15:51Z

Protected "Architecture - Commit on Share" ([edit=sysop] (indefinite) [move=sysop] (indefinite))

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Docadmin at 23:55, 18 January 2010

2010-01-18T23:55:11Z

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			'''''Note:''''' The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.

	== Summary ==		== Summary ==

Docadmin: /* Questions */

2010-01-14T22:05:27Z

Questions

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	* runtime control?		* runtime control?



	~~[[Category:Architecture\|Commit on Share]]~~

Docadmin: moved Commit on Share to Architecture - Commit on Share

2010-01-14T21:52:57Z

moved Commit on Share to Architecture - Commit on Share

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Docadmin: 1 revision

2010-01-14T21:01:09Z

1 revision

New page

== Summary ==

Commit-on-Share is intended to allow better recoverability in enviroment where clients miss reconnect window.

== Definitions ==

; '''Dependent transactions''': Two transactions are dependent if the second one cannot be executed until the first one is executed.
; '''Isolation''': defines level to which we consider transactions dependent:
* per-object -- all changes to same object are considered dependent,
* fine-grained -- some changes to same object are considered independent.
;'''Uncommitted object''': an object with changes cached and non-committed to disk.
; '''Dependency resolution''': remove request from replay queue committing it to persistent storage

== Requirements ==

# Provide with mechanism to avoid non-recoverable requests .
# Mechanism to be optional (runtime???) in order to allow users to choose between performance and reliability.
# No changes in wire protocol are allowed.
# Provide compatibility for old clients.

== Use Cases ==

{| cellspacing="0" border="1"
! ID !! Quality Attribute !! Summary
|-
| dependent request from same client
| performance
| performance shouldn't suffer with COS enabled
|-
| independent request from different client
| performance
| performance shouldn't suffer with COS enabled
|-
| dependent request from different client
| availability
| no dependency allowed after request execution, must be resolved before
|-
| set of independent requests
| availability, performance
| with fine-grained isolation request can be independent from all except some one
|-
| commit
| availability, performance
| commit event
|-
| CoS enable
| usability
| when and how we can enable CoS
|-
| CoS disable
| usability
| when and how we can disable CoS
|}

== Quality Attribute Scenarios ==

=== Dependent request from same client ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || Dependent request from same client
|-align="left"
|colspan=2|'''Business Goals:''' || application's performance doesn't drop
|-align="left"
|colspan=2|'''Relevant QA's:'''|| performance
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| application
|-align="left"
| '''Stimulus:'''|| request modifying file system
|-align="left"
|'''Environment:'''|| object has non-committed modification and new request depends on that
|-align="left"
|'''Artifact:'''|| a record for dependency tracker
|-align="left"
|'''Response:'''|| immediate execution, no dependency resolution is required
|-align="left"
|'''Response measure:'''|| roughly same performance as with COS disabled
|-align="left"
|colspan=2|'''Questions:'''||
|-align="left"
|-
|}

=== Independent request from different client ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || Independent request from different client
|-align="left"
|colspan=2|'''Business Goals:''' || application's performance doesn't drop
|-align="left"
|colspan=2|'''Relevant QA's:'''|| performance
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| application
|-align="left"
| '''Stimulus:'''|| request modifying file system
|-align="left"
|'''Environment:'''|| object has no modifications which new request depends on
|-align="left"
|'''Artifact:'''|| a record for dependency tracker
|-align="left"
|'''Response:'''|| immediate execution, no dependency resolution required
|-align="left"
|'''Response measure:'''|| roughly same performance as with COS disabled
|-align="left"
|colspan=2|'''Questions:'''||
|-align="left"
|-
|}

=== Dependent request from different client ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || Dependent request from different client
|-align="left"
|colspan=2|'''Business Goals:''' || prevent recovery failure if client doesn't re-connect in time
|-align="left"
|colspan=2|'''Relevant QA's:'''|| availablity
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| application
|-align="left"
| '''Stimulus:'''|| request modifying file system
|-align="left"
|'''Environment:'''|| object has non-committed modification and new request depends on that
|-align="left"
|'''Artifact:'''|| old dependency records are released, new one is created
|-align="left"
|'''Response:'''|| server resolves dependency flushing non-committed changes and suspend current operation till commit event
|-align="left"
|'''Response measure:'''|| performance degrades compared non-CoS
|-align="left"
|colspan=2|'''Questions:'''||
|-align="left"
|-
|}

=== Set of independent requests ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || Set of independent requests
|-align="left"
|colspan=2|'''Business Goals:''' || Allow few independent requests against same object to co-exist
|-align="left"
|colspan=2|'''Relevant QA's:'''|| performance, availability
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| application
|-align="left"
| '''Stimulus:'''|| few requests modifying file system
|-align="left"
|'''Environment:'''|| few clients issue requests against same object
|-align="left"
|'''Artifact:'''|| few records for dependency tracker
|-align="left"
|'''Response:'''|| immediate execution, no dependency resolution required, but each request should be checked it doesn't depend on any request from the set
|-align="left"
|'''Response measure:'''|| performance doesn't degrade significantly
|-align="left"
|colspan=2|'''Questions:'''|| is it really a requirement for current CoS?
|-align="left"
|-
|}

=== Commit ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || Commit
|-align="left"
|colspan=2|'''Business Goals:''' || Block dependent operations for as short as possible
|-align="left"
|colspan=2|'''Relevant QA's:'''|| availability, performance
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| underlying disk file system
|-align="left"
| '''Stimulus:'''|| all previous changes are committed to storage
|-align="left"
|'''Environment:'''||
|-align="left"
|'''Artifact:'''|| all dependencies become resolved
|-align="left"
|'''Response:'''|| dependency tracker get new "committed" border and continue suspended operations
|-align="left"
|'''Response measure:'''|| Dependency tables don't grow indefinitely
|-align="left"
|colspan=2|'''Questions:'''||
|-align="left"
|-
|}

=== CoS enable ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || CoS enable
|-align="left"
|colspan=2|'''Business Goals:''' || allow customers to control CoS
|-align="left"
|colspan=2|'''Relevant QA's:'''|| usability
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| administrator
|-align="left"
| '''Stimulus:'''|| request through control utility and/or procfs
|-align="left"
|'''Environment:'''|| CoS is disabled
|-align="left"
|'''Artifact:'''|| per-server flag enabling CoS
|-align="left"
|'''Response:'''|| since now dependency tracker checks whether coming operation depends on any uncommitted ones
|-align="left"
|'''Response measure:'''|| dependent operations are slow, but recovery during the server's reconnect window is guaranteed to succeed
|-align="left"
|colspan=2|'''Questions:'''|| do we need this run-time? if so, we need to take care of possible races here
|-align="left"
|-
|}

=== CoS disable ===

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' || CoS disable
|-align="left"
|colspan=2|'''Business Goals:''' || Allow customers to control CoS
|-align="left"
|colspan=2|'''Relevant QA's:'''|| usability
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''|| administrator
|-align="left"
| '''Stimulus:'''|| request through control utility and/or procfs
|-align="left"
|'''Environment:'''|| CoS is enabled
|-align="left"
|'''Artifact:'''|| per-server flag disabling CoS
|-align="left"
|'''Response:'''|| dependency tracker considers all operations independent since now
|-align="left"
|'''Response measure:'''|| dependent operations are fast, but recovery failure is possible in case of missed client
|-align="left"
|colspan=2|'''Questions:'''|| do we need this run-time?
|-align="left"
|-
|}

; '''QAS template'''

{|border=1 cellspacing="0"
|-align="left"
|colspan=2|'''Scenario:''' ||
|-align="left"
|colspan=2|'''Business Goals:''' ||
|-align="left"
|colspan=2|'''Relevant QA's:'''||
|-align="left"
|rowspan="6" writing-mode="vertical"|'''details'''
|'''Stimulus source:'''||
|-align="left"
| '''Stimulus:'''||
|-align="left"
|'''Environment:'''||
|-align="left"
|'''Artifact:'''||
|-align="left"
|'''Response:'''||
|-align="left"
|'''Response measure:'''||
|-align="left"
|colspan=2|'''Questions:'''||
|-align="left"
|-
|}

== Memos for HLD ==

# is it possible to cancel client's lock and do sync in parallel?

== Questions ==

* runtime control?

[[Category:Architecture|Commit on Share]]

Architecture - Commit on Share - Revision history

Docadmin at 21:00, 22 January 2010

Docadmin: Protected "Architecture - Commit on Share" ([edit=sysop] (indefinite) [move=sysop] (indefinite))

Docadmin at 23:55, 18 January 2010

Docadmin: /* Questions */

Docadmin: moved Commit on Share to Architecture - Commit on Share

Docadmin: 1 revision