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Old 10-07-2006, 08:51 PM   #1
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IDE/SCSI Declaration


I understand that Linux assigns the values /dev/hda to /dev/hdd for IDE devices. What I don't understand is what the values /dev/hda1 or /dev/hdb2, /dev/hdd4/, etc relate to and how they work. I would appreciate any help.

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Old 10-07-2006, 09:05 PM   #2
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The trailing numbers refer to the partitions. hda1 is the first partition of the first hard drive, hda2 is the second partition, etc.
 
Old 10-07-2006, 09:10 PM   #3
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IDE drives use hdxy for device IDs. y was described from your previous thread as the partition number. BTW an IDE drive can be divided into 64 partitions. x is defined as:
hda - 1st IDE controller master
hdb - 1st IDE controller slave
hdc - 2nd IDE controller master
hdd - 2nd IDE controller slave
and so on.

SCSI drives can be divided into 16 partitions and have devices IDs sdxy. Firewire, USB, SATA all use the SCSI subsystem modules and also have sdx device IDs. The first drive recognizced on the first controller recognizced is sda, next is sdb and so on. With udev it is possible to write rules so that a particular device is always the same device ID. This is good if you have several USB devices like a camera and a flash drive.
 
Old 10-07-2006, 09:20 PM   #4
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Thanks btmiller and michaelk. If devices are defined as:
hda - 1st IDE controller master
hdb - 1st IDE controller slave
hdc - 2nd IDE controller master
hdd - 2nd IDE controller slave

how do I know which defintion relates to which physical device? To my understanding each physical device is limited to 4 primary patitions and 64 logical paritions.
 
Old 10-07-2006, 09:33 PM   #5
michaelk
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Correction: 63 total partitions, 4 primary, 59 logical.
Primary partitions are 1-4, A logical partition is anything >4 i.e. 5-63.

I am not sure I understand your question. hda1 would be 1st partition on the master drive connected to the 1st IDE controller. All 4 primary partitions do not have to exist. i.e on a windows PC if you created a d: drive then typically it would be a logcial partition. Logical partitions start at 5 so
c: hda1
d: hda5
The extended partition if you remember from the previous thread is a container for logical partitions would be hda2.

hdb6 would be the 2nd logical partition on the slave drive connected to 1st IDE controller.

Last edited by michaelk; 10-07-2006 at 09:57 PM.
 
Old 10-08-2006, 12:31 AM   #6
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michaelk,

Thanks. So it is safe to assume that the following definitions are always true as well as that a logical partition is always greater than 4?

hda - 1st IDE controller master
hdb - 1st IDE controller slave
hdc - 2nd IDE controller master
hdd - 2nd IDE controller slave
 
Old 10-08-2006, 06:51 AM   #7
michaelk
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Yes it is.
 
Old 10-08-2006, 11:30 PM   #8
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michaelk,

Thanks for your help.
 
  


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