journaling | 易学教程

Can the data=journal mode of EXT4 avoid user data loss?

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问题 journal mode data=journal mode provides full data and metadata journaling. All new data is written to the journal first, and then to its final location. In the event of a crash, the journal can be replayed, bringing both data and metadata into a consistent state. This mode is the slowest except when data needs to be read from and written to disk at the same time where it outperforms all others modes. Enabling this mode will disable delayed allocation and O_DIRECT support. Here I have a few

Want to do an incremental backup for mongodb. Journaling? Oplog?

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问题 I want to daily backups for a single mongodb database, probably with mongodump. To not lose any data, I would like this to be incremental so if something goes wrong in the middle of the day, I need to be able to replay changes for that day up til the point of failure after doing a mongorestore. Am I understanding correctly that I need to use an oplog for this? Or is journaling the answer? I tried doing the following: Turning my mongo database into a replica set of just one, so that it creates

function to check if SQLite is using journal_mode=WAL or journal_mode=DELETE

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问题 I was looking for function which would help me to see which journaling mode is enabled.. I looked here too list of function There was function to check database status sqlite3_db_status(....) but status parameter didn't have option for check journaling mode Is there a function or any way to find if sqlite db is using WAL-mode or normal journaling mode ..!! 回答1: To query the journal mode of a connection, execute PRAGMA journal_mode and read the result. 来源： https://stackoverflow.com/questions

MongoDB Journaling : Is the journal file used when the client request a non journal write and journaling is activated on Mongod

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问题 I try to uderstand how journaling is exactly working : is that correct ? When no journaling is activated on the server side (mongod --nojournal) : (a) If the client request a journaled write it will output an error (from 2.6, before it was ignored), (b) If the client request a non journaled write, journaling will not be used so I guess change will be made on RAM, then the OS will flush changes to data file evry 60s. When journaling is activated on Mongod (mongod --journal (default on 64 bits

Prepopulated Core Data SQL store with new Write-Ahead Log (WAL) journaling

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问题 I would like to ship my app with an SQL datastore, but now, since Apple has introduced a WAL journaling, that makes 3 files instead of one, so I wonder if I should ship all 3 of them, or I can try to force SQL to make a checkpoint, merging it all into one .sql file. I would really like to go with this new iOS 7 feature, so going back to rollback journaling is not a way for me. 回答1: To force SQLite to make a checkpoint, execute PRAGMA wal_checkpoint. Alternatively, ship the database with

Want to use journaling enabled DB in 32 bit system-MongoDB

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问题 I want to run an existing application, that was developed earlier on 64 bit machine. It already has an existing database mongoDB with journaling enabled for 64 bit. In 32 bit system journaling is not enabled, so when I try to run MongoDB service with this DB, it does not work How can i reuse this DB and able to run this application in my 32 bit system? 回答1: You can manually enable journaling in 32bit MongoDB by starting mongod with the command line parameter --journal . When it still doesn't

Prepopulated Core Data SQL store with new Write-Ahead Log (WAL) journaling

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I would like to ship my app with an SQL datastore, but now, since Apple has introduced a WAL journaling, that makes 3 files instead of one, so I wonder if I should ship all 3 of them, or I can try to force SQL to make a checkpoint, merging it all into one .sql file. I would really like to go with this new iOS 7 feature, so going back to rollback journaling is not a way for me. To force SQLite to make a checkpoint, execute PRAGMA wal_checkpoint . Alternatively, ship the database with journal_mode = DELETE , and change the mode after the file has been installed. In any case, there is no problem

MySQL transaction journaling

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问题 I am working on a project for which we are required to use "transaction journaling" in our DBMS (MySQL). We have already switched to using InnoDB in order to use transactions for another requirement. I am trying to understand what transaction journaling is. I have been searching for over a day now, including reading through MySQL documentation. Maybe I am just not searching for the right keywords, I am not sure. Or maybe "transaction journaling" is inappropriate terminology. From what I