Time Machine 2tb limit?

btaroli wrote:

chirpa wrote: 2TB is the current limit. The filesystem on the NAS currently has a 2TB per file limit. Same limitation applies to regular files via CIFS/NFS/etc, even iSCSI targets. How is a per-file limit relevant to TM? TM creates sparsebundle packages (a folder) that contain several files as segments representing the entire volume. Therefore, it would stand to reason that any given segment might be limited to 2TB, but how does that translate to the whole sparsebundle?

Just what I was going to say. There is no way the Time Machine sparsebundle can cause file(s) to be bigger than 2TB since the segments are always smaller and are stored as individual files (as far as other operating systems are concerned).

It maybe that the 2TB limit is more an Apple limit in the TimeMachine client software. Since the biggest TimeCapsule is only 1TB and Apple don't ship any Macs with 2TB drives, they may not have thought of this. I wonder if Snow Leopard will address this. (Update - I believe the ReadyNAS is creating the TimeMachine partition as an image on the underlying EXT3 file system, and since EXT3 only allows 'files' up to 2TB in size, this limits the TimeMachine partition also to 2TB.)

For what it's worth, the 2TB limit in the ReadyNAS (for iSCSI for example) is due to the ReadyNAS currently using EXT3 as the underlying file system. See http://en.wikipedia.org/wiki/Comparison_of_file_systems for a comparison of the limits of file systems.

I would guess NetGear are planning on moving to EXT4 although from a Mac point of view ZFS might be a better long term choice since Apple is adding (some) ZFS support in Snow Leopard.

PS. Old though HFS+ might be, it already supports files of nearly 8 Exabytes, way more than even EXT4 which 'only' supports 16 Terabytes. ZFS supports files up to 16 Exabytes. NTFS is not too shabby either, it also supports up to 16 Exabytes. So EXT4 looks a pretty short-term fix.