The Linux 64 GiB Limit - was: Re: oops! Should be fdisk broken?

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  • The Linux 64 GiB Limit - was: Re: oops! Should be fdisk broken?
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Guest section DW Jan. 25, 1999, 10:26 p.m. UTC
> 	From: David Hamm <>
> 	 I have an 84g raid unit I'm trying to fdisk.  When the computer boots I get
> 	the  following info on the drive. 
> 	SCSI device sdb: hdwr sector= 512 bytes. Sectors= 164659200 [80400 MB] [80.4 GB] 
> 	When I fdisk it I get different info and after partitioning and mke2fs the 
> 	dirve only mounts with 14g of space.  I know this is a geometry issue but why 
> 	is it an issue?  Can fdisk be fixed? 
> Not if you do not provide any detail at all.

	From Mon Jan 25 16:48:31 1999
	From: David Hamm <>

	Disk /dev/sdb: 64 heads, 32 sectors, 14864 cylinders

Aha! Very good. You lost precisely 2^27 sectors, that is 64 GiB,
or, more relevant, 2^16 cylinders.

No surprise, since cylinders is a short.

So, the following should improve things. (Unverified, untested.)


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--- hdreg.h~    Fri Jan 22 16:49:34 1999
+++ hdreg.h     Mon Jan 25 23:13:06 1999
@@ -114,7 +114,7 @@ 
 struct hd_geometry {
       unsigned char heads;
       unsigned char sectors;
-      unsigned short cylinders;
+      unsigned long cylinders;
       unsigned long start;