Maximum Number of Partitions

rls · 2003-09-01 14:31:23

I cannot find a good reference for the maximum number of partitions possible on a single hard disk. One source said 64 partitions were possible, i.e. /dev/hda1 to /dev/hda64. I have seen /dev directories with hda1 to hda32 entries. I have read that 19 partitions are possible, three primary partitions, hda1 to hda3 and 16 logical partitions, hda5 to hda20 under the extended partition hda4. Not all can be right.

If anyone can point me to a clear, authoritative reference, I would be most appreciative.

Regards, Rick

netkrash · 2003-09-01 14:38:35

i know that can be only 4 partitions using the standar primary partitions..

but there logical/extended partitions and i don't know how many parts are possible with this

rls · 2003-09-01 16:56:41

Perhaps I can answer my own questions, assuming /usr/src/linux/Documentation/devices.txt is the horses' mouth. An IDE disk can contain 64 partitions, labelled hdx1 to hdx64, where x is the appropriate letter. With the maximum number of partitions hdx1 to hdx3 would be the primary partitions, hdx4 the extended partition, and hdx5 to hdx64 the logical partitions. Thus one would have 64 partitions and 63 usable ones.

I presume that only having /dev/hdx1 to /dev/hdx32 results from a setup decision based on the concept that 32 partitions suffice. And that /dev/hda33 to /dev/hda64 could be added later "by-hand" if one needed them.

A SCSI hard disk can only have 16 partitions. So for the maximum number of partitions, sdx1 to sdx3 would be the primary partitions, sdx4 the extended partition and sdx5 to sdx16 the logical partition.

Regards, Rick

dp · 2003-09-01 16:59:33

in the MBR, precisely in the 447 to 508 bytes is your partitiontable, the true one --- containing only 4 entries

one of them can be an "extended" partition (0x05): this means only that in the partitiontable (in the mbr) there is a entry that says: "and the rest is a big unformated partition that has a special handling".

The extended partition is divided into segments that are treated as a logical drive and formatted with a file system.

Each logical partition has a pointer to the next logical partition, which implies that the number of logical partitions is unlimited (theoretically!!!).

-> if you write a harddisk-driver by your own, you can have really a lot of partitions. :-)

However, the linux-kernel imposes limits on the total number of any type of partition on a drive, so this effectively limits the number of logical partitions. This is at most 15 partitions on an SCSI disk and 63 on an IDE disk. WindowsNT4Server has a 32 logical partition limit. For the other OS's i dont know the drivers, but i assume, they are also limited, because of optimizing.

EDIT: sorry to repeat some data, but didnt realize that rls did answer at the same time

rls · 2003-09-03 14:20:20

Thanks for the info.

Rick

Arch Linux

#1 2003-09-01 14:31:23

Maximum Number of Partitions

#2 2003-09-01 14:38:35

Re: Maximum Number of Partitions

#3 2003-09-01 16:56:41

Re: Maximum Number of Partitions

#4 2003-09-01 16:59:33

Re: Maximum Number of Partitions

#5 2003-09-03 14:20:20

Re: Maximum Number of Partitions

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