• This feature is available since Osiris 1.7.2


Customers who encounter performance issues with Osiris volumes can manually adjust the block size and io size of Osiris via the config.


1. Uninstall the previous Osiris version using the Osiris uninstaller:
2. Install Osiris 1.7.2 or a newer version of Osiris.

3. Keep Osiris closed!

4. Now you can add the below lines to the Osiris config /Users/Shared/Preferences/osiris/config/osiris.json. On the bottom of this page is an example config that shows you where to place these values.

"block_size": 4096,
"io_size": 8192,

5. The block_size should match your storage block size and the io_size should be a multiple of it. Both values must be provided in bytes. E.g. Stornext 5 uses a block size of 4k, so block_size should be 4096 (4 × 1024) and io_size should be at least 8192 (2 x “block_size”).

6. Open Osiris

7. Mount a volume and check in the Osiris log if the values have been applied. The log is located under /Users/Shared/Preferences/osiris/logs/Osiris-current-date.log and the output you are looking for looks like this:

[Info    13:19:03.385] Settings configuration file path: /Users/Shared/Preferences/osiris/config/osiris.json
[Info    13:19:03.387] Block size from the config: |4096|
[Info    13:19:03.387] IO size from the config: |8192|

Config Example

    "save_config_on_exit": false,
    "block_size": 4096,
    "io_size": 8192,
    "volumes": [
            "name": "alex",
            "src_path": "/Volumes/sb-global/folder1/"
            "name": "hello",
            "src_path": "/Volumes/sb-global/folder2/"
Last modified: May 23, 2022

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