Re: VFS/ext2fs - large files on the Alpha (fails for 17GB+)

Matti Aarnio (matti.aarnio@sonera.fi)
Thu, 20 Aug 1998 09:17:11 +0300 (EEST)


Alex Buell <alex.buell@tahallah.demon.co.uk> wrote:
...
> Does that means we *can* have a disk partition (or a RAID system) with a
> max. size of 70TB with ext2fs on Intel platforms with a block size of 8192
> bytes? If so, will that be enough to satisfy one's lust for ever expanding
> disk space....

Umm... Propably not. While the theorethical block addressability
goes up like (blksize/4)**3 function, the maximum offset encodable
with blocks is different (non-exponential) function:

32-bits per block offset within FS, giving us 4G blocks maximum.
blksize offset (blksize/4)^3 max size
1k 4 TB 16 GB 16 GB
2k 8 TB 256 GB 256 GB
4k 16 TB 4 TB 4 TB
8k 32 TB 64 TB 32 TB
So, you can't have 70TB filesystem with EXT2 even if you had the
hardware... (counting with 1024 byte kilos that is 64 TB)

Also I think that at Intel you are better off to limit yourself
to 4k blocks as those match paging system page size, and using
larger blocks than pagesize is rather difficult...

> Cheers,
> Alex
> --
> http://www.tahallah.demon.co.uk

/Matti Aarnio <matti.aarnio@sonera.fi>

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