The maximum LUN size in iSCSI can be up to 250 TB, but this depends on system specifications and available RAM.
Here's a breakdown:
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Maximum theoretical limit: The iSCSI protocol itself can support much larger LUN sizes, potentially into the exabyte range. However, practical limitations imposed by operating systems, file systems, and hardware usually restrict the maximum usable LUN size.
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Practical limitations:
- System RAM: If the NAS or storage device has less than 4GB of RAM, the maximum LUN size may be further limited (e.g., to 144 TB).
- Operating System: Different operating systems (Windows, Linux, etc.) and their respective file systems (NTFS, ext4, XFS) have their own limitations on maximum volume and file sizes, which in turn affect the maximum usable LUN size.
- File System: The choice of file system directly impacts the maximum supported LUN size.
- Hardware: RAID controllers, HBAs (Host Bus Adapters), and other hardware components also have limits on the size of the storage they can manage.
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Important Considerations:
- Performance: Larger LUNs can sometimes impact performance, especially with older or less performant hardware. It's crucial to consider the application's I/O requirements and choose a LUN size that balances capacity and performance.
- Backup and Recovery: Larger LUNs can take longer to back up and restore. Consider backup strategies and recovery time objectives (RTOs) when planning LUN sizes.
- Vendor Recommendations: Consult the documentation and recommendations from your storage vendor for specific maximum LUN size limits and best practices.
Therefore, while 250 TB is a commonly quoted maximum, it is crucial to consider your specific hardware, software, and performance needs when configuring iSCSI LUNs. Always refer to the documentation for your specific storage solution to determine the actual maximum LUN size supported.
