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What is the maximum number of partitions we can make on hard disk in Windows?
If it is limited to some particular number, why can we assign all the letters C through Z to drives? If it is a special case, what's that?
raj
Posted 2011-12-15T03:34:19.467
Reputation: 551
44
On the legacy "MBR" partitioning scheme, you can have 4 primary partitions, or 3 primary partitions and one extended partition containing any number of logical partitions. While you can assign a drive letter to a partition, you can also map it as a folder in current versions of Windows, allowing more partitions, or use subst to mount it to a number.
The EFI specification mandates that a GUID Partition Table (GPT), which all modern operating systems support, is capable of containing a maximum of 128 partitions on any size hard disk. GPT is also required to boot from hard disk drives larger than 2 TB. This partitioning scheme is now widely used with UEFI being natively supported by practically all new computers.
In addition to native partitions, Windows and Linux also have something called a "logical volume manager", which can overlay dozens, if not hundreds of virtual partitions (logical volumes) on top of the 4 (MBR) or 128 (GPT) physical partitions. Logical volumes can be assigned drive letters or mountpoints in the same way as physical partitions. They can also be bootable if certain constraints are met.
It's also possible to have GPT-formatted disks on non-UEFI systems, and MBR disks on UEFI systems (with the exception of the boot disk).
Journeyman Geek
Posted 2011-12-15T03:34:19.467
Reputation: 119 122
"In Linux ... partitions are a non-issue" -- while you're more insulated from the raw partition structure, they still are significant for many purposes - including legacy bootloaders, the ESP for UEFI boot, software RAID, encrypted volumes, etc., etc.. Legacy bootloaders are the one place where a "primary" partition is important/required. – Bob – 2016-03-25T09:58:25.303
Be Watchful! Though GPT partitioning scheme (& MBR logical drives) does allow 128 partitions but u can't assign drive letters to all of them once u have consumed 26 letters of English alphabet. So from 27th drive onward you have to follow volume ID scheme as described here which will not be so easy to use for normal users. Since few drive letters are also consumed by your DVD Drive, thumb drive or any network mounted drive so drive letters can get exhausted bit earlier also. – RBT – 2016-10-26T06:16:37.597
3Isn't it the other way around? One extended partition containing any number of logical ones? – avakar – 2011-12-15T07:31:38.767
1my bad ;p fixed – Journeyman Geek – 2011-12-15T07:57:18.280
74 partitions is the MBR scheme. Other schemes are out there. – mouviciel – 2011-12-15T08:14:05.390
1Ya, not gotten to play with GPT or BSD Slices yet. – Journeyman Geek – 2011-12-15T08:17:49.750
The support for partitions isn't much different on Windows than on Linux. Both have to respect the limits of MBR if the hard disk is set up that way - you can't bypass MBR limits simply by using Linux. Try to dual boot Windows 7 (needing two partitions by default - main and restore) and Linux (often wanting three partitions by default - system, user and swap) can be a problem if you don't plan ahead before you start installing. – Steve314 – 2011-12-15T10:56:06.050
1@Steve314, you can remove Window's system maintenance partition and even prevent it from creating it. Also, both Linux and Windows can boot from logical partitions just fine, just the bootloader has to be on a primary partition (a small partition with GRUB will make that trivial). – Mircea Chirea – 2011-12-15T12:31:25.730
@iconiK - mostly true, but the Windows 7 install disks I've used (all Home Premium OEM) didn't allow an install without that maintenance partition or offer any other options. When I installed on a hard disk with three Linux partitions already present, the install failed - ran as far as the first reboot, then gave a "hard disk read error" instead of running the bootloader, leaving even the existing operating system unbootable. Similar issues happen installing with a single Windows XP logical partition already present. The issues can be worked around, but as I said, you have to plan ahead. – Steve314 – 2011-12-15T15:40:44.917
Your comment "you just need to have enough device letters" is incorrect. You can have more than 26 drives. After sdz => sdaa => sdab => sdac etc. This pattern will continue forever as far as I know. – tbenz9 – 2013-08-21T18:39:34.880
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On a disk using the traditional MBR format, the partition table has four slots. Each can hold a "primary" partition, or one can be used to create an "extended" partition which can contain any number of sub-partitions (often called "logical drives"). Extended partitions are basically a workaround for the small size of the MBR partition table, and there are limitations on what they can be used for. (For example, the Windows bootloader must be on a primary partition.)
The newer GPT disk format supports many more partitions — technically unlimited, I think, but operating systems impose a limit of 128. These are all "primary" partitions (to use the MBR terminology).
Wyzard
Posted 2011-12-15T03:34:19.467
Reputation: 5 832
I'm totally out of touch with GPT. Looks like i have some learning to do ;p – Journeyman Geek – 2011-12-15T05:07:24.790
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From Technet: Reviewing Storage Limits: Local File Systems:
The number of disk drives you can use for each server is limited only by the available memory for FAT16, FAT32, NTFS, and UDF files systems.
So no there is no hard limit on Windows on the number of drivers. Drive letter are of course limited, since they stop at Z. But drives don't have to be given a drive letter - they can be mapped to a folder on another drive. From the same Technet article:
Mounted drives are useful when you want to add more storage to an existing volume without having to extend the volume. A mounted drive is a local volume attached to an empty folder on an NTFS volume. Mounted drives are not subject to the 26-drive limit imposed by drive letters, so you can use mounted drives to access more than 26 drives on your computer. For more information about mounted drives, including information about creating mounted drives on server clusters, see "Using NTFS mounted drives" in Help and Support Center for Windows Server 2003.
shf301
Posted 2011-12-15T03:34:19.467
Reputation: 7 582
34 upvotes, and it doesn't answer the Qs!? The question is about partitions not drives. – sawdust – 2011-12-15T06:09:56.063
1actually original question title said drives, it was edited to partitions, since , well, considering context, it was more correct. – Journeyman Geek – 2011-12-15T08:17:20.683
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Hard disks can be split into four primary partitions, or one of these can be configured as an extended partition.
An extended partition can theoretically contain an infinite number of logical partitions, and so while Windows only has drive letters up to z: (plus some other characters) this is not a limit on the number of partitions you can create, even if you can't assign a drive letter to them.
Paul
Posted 2011-12-15T03:34:19.467
Reputation: 52 173
4While this is true for disks with an MBR partition table, this is incorrect for disks with a GPT partition table. – Darth Android – 2011-12-15T03:56:41.670
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If the drive is partitioned using GPT, windows can only handle 2 for the following reason. When GPT is employed, each primary partition has another hidden partition to go with it called EFI. When Windows sees this EFI partition, it counts as 1 primary. So 2 partition in GPT means 4. This is a sad limitation for Windows when testing a new build using GPT scheme. Linux and OS X is far more flexible.
tdt-modifier
Posted 2011-12-15T03:34:19.467
Reputation: 19
0
Maximum slices allowed on windows mbr is 4.
Loosely called as "partitions", means 4 paritions. However, any one of these 4 partitions, ie one and only one of them can be extended further into "partitions" or logical drives. In summary, it is said as 3 primary partitons and one "extendable" partition. The "extendable" partition as logical drive can only go with the letters a to z. As the alphabet a and b are used for floppy drives, only c to z is available for use.
comgreen
Posted 2011-12-15T03:34:19.467
Reputation: 1
Drive letters do not limit the number of partitions Windows can handle. You can mount volumes as directories under other drive letters. – Ben N – 2016-02-21T23:57:12.167
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Theoretically, an unlimited number of partitions can be created in a drive. The total number of partitions is limited by the amount of space that is reserved for making partition entries.
ranvir
Posted 2011-12-15T03:34:19.467
Reputation: 11
-1 for being quite wrong. The theoretical limits are calculable with some simple arithmetic and are very much finite. – JdeBP – 2011-12-23T11:15:38.680
7The number of partitions per hard disk isn't relevant to the number of drive letters, since there may be more than one hard disk in a system. (Also drive letters are used for other things such as mapped network shares.) – Harry Johnston – 2011-12-15T20:41:06.790