@bc-consultancy
Thank you for your post!
When it comes to increasing your Azure Sentinel data retention, I found some Tech Community blogs that will detail how logs from a Log Analytics workspace can easily be moved into long-term cold storage in order to comply with retention standards as well as reduce cost.
Using Azure Data Explorer for long term retention of Azure Sentinel logs
Move Your Azure Sentinel Logs to Long-Term Storage with Ease
I hope this helps, if you have any other questions, please let me know.
Thank you!
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