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Hard drive partition question

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September 1, 2007 5:31:55 PM

Hello all,

Previously while partitioning a disk under DOS, the options were to create a primary and an extended partition with options of having multiple logical drives in the extended partition. Now in the Disk Manager of XP or Vista, I can see that although the option of extended partition is there, I can actually create multiple primary partitions in the same drive.

Could someone please explain the benefits or drawbacks of having an extended partition with logical drives as opposed to just having multiple primary partitions please?

Also, does it make a difference for windows while assigning drive letters?

Thanks in advance.

DM
September 1, 2007 6:49:57 PM

The MBR standard allows a maximum of 4 primary partitions per disk, and the extended partition container that has extended logical partitions in it is itself considered one primary partition.

DOS-based OS's (DOS, Win95, 98, ME) would not boot properly with more than one primary partition per disk (not counting the extended partition). That's why it used to always be recommended that if you wanted more than one partition on a physical disk, that one partition (the bootable one) be a primary partition, and the rest be extended partitions.

Under Windows NT, 2K, XP, 2K3, Vista, that is no longer necessary - these OS's handle multiple primary partitions with no problem. These OS's will also allow you to arbitrarily assign drive letters to partitions regardless of the physical order that they appear on the disk.

Because of that flexibility, hardly anyone uses extended partitions anymore. The only reason to use it would be if you needed more than 4 partitions on the disk - then you have to make all partitions beyond #3 as a logical partition inside an extended partition.
September 1, 2007 7:43:23 PM

Thank you for a very informative answer.
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September 26, 2007 6:02:54 PM

- SomeJoe7777 "Because of that flexibility, hardly anyone uses extended partitions anymore. "

Such a strong statement. Actually a lot of people use Extended partitions for all sorts of reasons.

I use 500GB and 1TB size drives for a lot of digital imaging data and use logical partitions to segregate different projects, clients and data content. One reason I do this is it makes information easier to manage, search etc..., other reasons; makes backups quicker, makes defragmentation quicker etc.

I happened across this post today that gives some additional reasons, more form a technical standpoint.
http://www.msfn.org/board/Partitions_Primary_Logical_t33964.html

Kevin Erskine
KErskine@Software-By-Ragazzi.com
September 28, 2007 3:25:47 AM

Kerskine said:
Such a strong statement. Actually a lot of people use Extended partitions for all sorts of reasons.

I use 500GB and 1TB size drives for a lot of digital imaging data and use logical partitions to segregate different projects, clients and data content. One reason I do this is it makes information easier to manage, search etc..., other reasons; makes backups quicker, makes defragmentation quicker etc.

I happened across this post today that gives some additional reasons, more form a technical standpoint.
http://www.msfn.org/board/Partitions_Primary_Logical_t33964.html


I didn't mean that people hardly use partitions anymore. I meant that people hardly use logical partitions anymore (logical partitions are also sometimes called extended partitions, because back in the DOS days they extended the capability of partitioning past 4 partitions). You use them because of the exception that I cited at the end of my last post -- due to the way you organize your data, you need more than 4 partitions per disk, and the only way to do that is with logical partitions.

Many people use partitions these days to organize data (especially for things like keeping the OS separate from other data), however most people don't use more than 4 partitions per disk. Thus for them, logical/extended partitions aren't necessary, only primary partitions are.

I don't agree with a lot of the points in the technical post you cited - I disagree that track 0 of the hard disk is accessed more than other tracks (the MBR and partition table are cached into memory when Windows is running, and Windows never goes back to re-read the MBR and partition table unless something needs to change it -- like Windows Disk Management). If a virus intentionally wipes your hard drive and destroys track 0, you're looking at data recovery, no matter if you're using primary partitions or logical/extended partitions. Besides, most viruses these days are designed for adware or spam delivery, not malicious data destruction.
a b G Storage
September 28, 2007 4:02:36 AM

The best thing to do is this:

HDD#1: OS and programs
HDD#2: Data

I always keep my OS on a seperate drive than my data. Also, XP only will handle 4 primary partitions anyway.
September 28, 2007 9:03:21 PM

runswindows95 said:
The best thing to do is this:

HDD#1: OS and programs
HDD#2: Data

I always keep my OS on a seperate drive than my data. Also, XP only will handle 4 primary partitions anyway.


That is the best thing for you. It is not necessarily the best thing for other people, because they may not have the same goals as you.

The 4 primary partition limit is not imposed by Windows XP. Windows XP will handle a large number of primary or logical partitions. It is a limitation of the MBR partitioning scheme used by 99% of all computer BIOS's, as I discussed in the 2nd post in this thread.
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