Anaconda, parted, and geometry

Robert L Cochran cochranb at speakeasy.net
Fri Nov 7 03:38:26 UTC 2008


I checked the Lenovo website. Removing the T61's hard drive is really
simple to do. I suppose you don't have a solid state drive, right? And
you can check on the Lenovo forums for why the drive geometry is set
this way and how to change it back to a standard configuration. Your
laptop's documentation probably says something too.

Bob Cochran


Robert L Cochran wrote:
> I wonder -- if this is an IDE hard drive, do the jumpers on the drive
> allow you to change the default geometry? It seems to me that BIOS
> interrupt 13h would need to know this same information and it may be
> there is a BIOS setting for it too. But I bet the hard drive itself may
> let you set the geometry with a jumper or two. So I'm suggesting you
> first check the BIOS settings and if need be de-install the hard drive
> check for this and see if you can rearrange the jumpering to allow a
> more vanilla 255/63/63 CHS arrangement.
>
> Be real careful to remember exactly where pin 1 is if this is an IDE
> drive. And be real tender with those drive pins. Don't bend one into a
> noodle shape. That has happened to me.
>
> Bob Cochran
>
>
>
> Chuck Anderson wrote:
>   
>> For reasons known only to IBM, Thinkpads have been shipping with hard 
>> disks partitioned with a geometry of 240 heads, 63 sectors.  Even my 
>> brand shiny new T61 does this.  However, since Linux has stopped 
>> asking the BIOS what geometry to use, it now defaults to 255 heads, 63 
>> sectors.  Further, it isn't clear to me how to override Linux's choice 
>> of hdd geometry in the new world order of libata, nor should that be 
>> necessary in the normal case to get a sane partition table IMO.
>>
>> Why should I care, you ask?  Isn't disk geometry an anachronism from 
>> the days of DOS?  Well, yes, but the problem is for whatever reason, 
>> not everything ignores geometry...
>>
>> For example, Anaconda/parted likes to force cylinder alignment.  
>> Windows uses the BIOS/partition table geometry which may have a 
>> different idea about where cylinders begin and end.  The reasons for 
>> these behaviors aren't entirely clear to me.
>>
>> This leads to /really/ weird partitioning when different programs with 
>> different ideas of the geometry add/delete partitions from the disk, 
>> such as strange gaps of free space when you create a new partition in 
>> Anaconda, or situations where some partition table entries are stored 
>> using one set of C,H,S values, and others are using a different set. 
>> This of course also causes programs like "fdisk" and "sfdisk" to 
>> complain about cylinder boundaries and C,H,S values being incorrect.
>>
>> What to do about it?  Can't we all agree to use the same geometry when 
>> dealing with the partition table?  When Anaconda/parted reads the 
>> table, shouldn't it deduce the most fitting C,H,S values to use for 
>> cylinder alignment and writing out new entries?  Or shouldn't it ask 
>> the BIOS what to use, since that seems to be what Windows does?
>>
>> I used to work around issues like this by using fdisk in VT2 to 
>> partition things how I like, and then let Anaconda install to those.  
>> However, it now seems impossible to create a new encrypted LVM PV 
>> unless you let Anaconda's parted create the PV partition too.  Perhaps 
>> that could be improved upon.
>>
>> I remember a bit of the fiasco of "I can't boot Windows anymore" that 
>> happened a few years ago, but I don't know what the outcome/solution 
>> was.  Did the Linux kernel and Anaconda just punt the whole issue of 
>> trying to match geometries and let things fall as they may?
>>
>> Whatever was done, it just seems wrong and dirty to end up with a disk 
>> that has a schizophrenic idea of what geometry to use for its 
>> different partitions.
>>
>> --Chuck, who had to create a spreadsheet just to figure out what 
>> happend to his partition table...
>>
>>   
>>     
>
>   




More information about the fedora-test-list mailing list