Codacy Cleanup of documentation
As part of fixing the codacy warning
during the pre-merge job.
![image](./Images/9_Dataflow_with_Metadata)
# DTM
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+ DTM: Distributed Transaction Manager
+ CORTX operations affect multiple nodes. Nodes can fail independently. Error recovery is difficult.
+ Multiple CORTX operations form logical groups:
![image](./Images/10_DTM.png)
# DTM Implementation Overview
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+ Track distributed transactions for each operation (send transaction identifier)
+ Each service, before executing the operation, writes its description into FOL: file operations log
+ In case of a service or a client failure, surviving nodes look through their logs and determine incomplete transactions.
+ Fortunately, in DTM0 re-do is always possible
# FDMI
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+ FDMI: file data manipulation interface, CORTX core extension interface
+ CORTX core: objects, key-value indices, transactions. Fast path
+ Extensions: migration, backup, archive, replication, compression, encryption, indexing, tiering, defragmentation, scrubbing, format conversion, re-striping, etc.
![image](./Images/11_FDMI.png)
# FDMI Implementation Overview
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+ FDMI is a scalable publish-subscribe interface
+ Each CORTX core instance produces cross-referenced records describing operations stored in FOL
+ FDMI plugin registers a filter, that selects some records
![image](./Images/12_FDMI_Implementation_Overview.png)
# FDMI example plugin: integrity checking
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+ How to recover from catastrophic failures?
+ Redundancy, fancy metadata: not an answer (has been tried)
+ bugs (more important over time)
+ hdf5
# ADDB
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+ ADDB (analytics and diagnostics data-base): built-in fine grained telemetry sub-system
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+ Why?
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+ systems grow larger and more complex
+ how well the system is utilized?
+ is it failure or expected behavior?
# ADDB: advanced use cases
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+ collect system execution traces
+ use them to calibrate a simulator
+ use the simulator to:
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+ model systems before hardware is available (very large, very fast)
+ answer "what if?" questions
+ combine workloads
![image](./Images/15_ADDB_Advanced_Use_Case.png)
# Questions
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