On 6/9/14, 1:03 PM, Mahesh Khanwalkar wrote:
> Hello,
> Ext4 supports max file size of 16TiB and max volume of 1EiB. What
> exactly in the implementation causes this restriction? Also is there
> any plans (as of now) to make it max sizes larger?
The ext4 extent format on disk is:
struct ext4_extent {
__le32 ee_block; /* first logical block extent covers */
__le16 ee_len; /* number of blocks covered by extent */
__le16 ee_start_hi; /* high 16 bits of physical block */
__le32 ee_start_lo; /* low 32 bits of physical block */
};
The file size is limited by a 32-bit number for the starting logical block
of an extent, ee_block.
2^32 * 4k blocks gives 16TiB
The 48 bits for physical start high/low gives you the 1 EiB (2^48*4096).
I don't know of any plans to make either of these larger. Surely 1EiB
suffices for now. 16TiB, perhaps not so much.
-Eric
> Thanks,
> Mahesh Khanwalkar
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