Question & Answer
Question
How to use nzbackup argument FSYNC_DEST_BYTES along with PDA appliance.
Note: For Netezza Performance Server (NPS) please use this technote instead
Cause
FSYNC_DEST_BYTES is a Netezza file system backup connector option that throttles the host writes to an external file system by flushing the modified buffers after a specified number of bytes and waiting for the device to finish.
This option helps to reduce incidents where the Pure Data for Analytics host restarts and fails over while writing data to a slow external file system.
Answer
You use the FSYNC_DEST_BYTES option to set the maximum amount of data that will be buffered before flushing to the destination drive. For example:
Note that using this option may increase the overall time of the backup process, so you don't have to use this option unless file system backups are causing your NPS host to restart.
How to choose the best value for your backup operation?
There are no default values and you must try them to value the impact on the backup operations. These are the points to consider.
Available in the following releases and onwards.
Delivered to [7.2.0.5]
Delivered to [7.2.1]
nzbackup -dir /home/user/backups -u user -pw password -db mydb -connectorArgs FSYNC_DEST_BYTES=524288000
Note that using this option may increase the overall time of the backup process, so you don't have to use this option unless file system backups are causing your NPS host to restart.
How to choose the best value for your backup operation?
There are no default values and you must try them to value the impact on the backup operations. These are the points to consider.
- Start by using sync every 100-500MB (104857600 - 524288000)
- If you decrease the value of the parameter, the synching mechanism will be called with less bytes. Smaller writes means more of them, and that will increase the the overall backup time.
- If you increase the value of the parameter, the backup time will probaly not change, but the Host failover problem might appear during the backup process.
Available in the following releases and onwards.
Delivered to [7.2.0.5]
Delivered to [7.2.1]
Related Information
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Document Information
Modified date:
04 September 2023
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