# SATA disk partition name limit (15) questions

## wrc1944

Does anyone know if the SATA disk partition name limit of 15 has been fixed (increased)? Apparently, I have run up against this on a box with two 250GB Seagate SATA disks, where it won't allow me to format sda16 which I created with cfdisk. Mkfs.ext3 /dev/sda16 says sda16 "does not exist." Nothing else works either- gparted, fdisk, Partiton Magik, etc., windows or Linux.

I use sdb for winXP with a Sonar pro audio setup (5 partitions), and sda for my main dual boot winXP and Gentoo installations (8 total partitions), and PCLOS and 64studio distros, which totals up to sda15. I'd like to also be able to test many various multiple distros on this box, and with 500GB total disk space, this SATA drive 15 partition limit seems ridiculous, especially when older IDE drives don't have this low of a limit.

Is this merely an unaddressed kernel problem with the SATA divers/modules that can be fixed with a patch, or is it an inherent limitation of the SATA hardware itself? I've googled around, looked at the kernel patch pages, etc., with no clues.

Are SATA disk users (now basically the new standard) doomed to never be able to create more than 15 partitions, or am i missing something obvious?

----------

## NeddySeagoon

wrc1944,

Its a kernel limit for all SCSI drives. There are only 16 minor device numbers allocated per SCSI device, thats the whole device and 15 partitions. If you really want to be nonstandard, you can hack on the kernel.

less /usr/src/linux/Documentation/devices.txt says

```
   8 block       SCSI disk devices (0-15)

                  0 = /dev/sda          First SCSI disk whole disk

                 16 = /dev/sdb          Second SCSI disk whole disk

                 32 = /dev/sdc          Third SCSI disk whole disk

                    ...

                240 = /dev/sdp          Sixteenth SCSI disk whole disk

                Partitions are handled in the same way as for IDE

                disks (see major number 3) except that the limit on

                partitions is 15.

```

so block device (8,16)  would be /dev/sdb, not /dev/sda16.

There are ways round the issue in Linux. Explore the use of LVM2

----------

## wrc1944

NeddySeagoon,

Thanks very much for the quick info! I'll look into LVM2- haven't really thought about it before.

Am I to understand a kernel hack (patch) could increase the number of devide numbers on SCSI drives?

If so, it seems curious that kernel developers/hackers haven't addressed this issue long ago.  I'm not sure I'm knowledgable enough myself to attempt this level of stuff. I can edit kernel source files and patch diffs OK, but only if I know from another source what I'm supposed to be doing.    :Wink: 

----------

## NeddySeagoon

wrc1944,

I don't think its a lot of work but it would either break backwards compatibility or need new major device numbers to be allocated (or both)

----------

## Vlad

Kernel hackers haven't addressed this because it's not really an issue.  Very, very few people use so many partitions on a typical workstation.  Of course, it could be argued that new volume managers like LVM itself are addressing this 'issue'.  Have you ever considered using virtualization software instead for testing distros?  Why on earth are you using so many partitions?  (Not trying to be critical, I'm actually quite curious...other than the obvious reason of testing multiple distros/dual booting XP)

----------

## wrc1944

Vlad,

As an example, here is my current setup on a 120GB Seagate SATA backup drive I use for fooling around on (lots of distro testing- currently trying out the audio distros 64studio and Jacklab).

The first FAT32 section is from when my main drive was failing on my original Windows pro audio installation 2-3 years ago, and I had to clone the entire setup over as a backup.

The 2nd section is one of my main Gentoo ~x86 installs, where I play around with newest kernels and audio app betas.

The third section is where I install and remove lots of new versions of the distros I like to check out- but Gentoo is my main distro for about 4 years now.

Name          Flags      Part Type     FS Type                     [Label]       Size (MB)

 -----------------------------------------------------------------------------------------------

sda1                          Primary       W95 FAT32                  C:            8398.02

sda5                          Logical        W95 FAT32                  Sonar       21188.33

sda6                          Logical        W95 FAT32                  Audio        382.82

sda7                          Logical        W95 FAT32                  Images      4968.07

sda8                          Logical        W95 FAT32                  Backups     5510.94

sda9                          Logical        Linux ext2                    boot              98.71

sda10                        Logical        Linux swap / Solaris      swap             1003.49

sda11                        Logical        Linux ext3                    home            6999.72

sda12                        Logical        Linux ReiserFS              /usr/portage  5000.98

sda13                        Logical        Linux ext3                          /             10001.95

sda14                        Logical        Linux ext3                 /mnt/PCLOS    11679.90

sda15                        Logical        Linux ext3                 [64studio]       10997.20

sda3                          Primary       Linux ext3                 /data               12740.96

sda4                          Primary       Linux ext3                 /jacklab          15085.17

This drive has been messed around with reformatting different partitions, resizing, moving, etc. depending on what I wanted to do at the time, that the sizes and where stuff is located has gotten into a state that might seem a bit weird.  All my distros always share the same swap partition, and I always use my Gentoo grub, and chainload everything else into it's own grub (on it's own /).  I found that the best way, since I'm constantly changing Gentoo kernels, and I never remove Gentoo anyway.

Anyway, that's the rationale for my having many partitions. I guess you're right- this is not really an issue for the vast majority of users.  I really need to look into LVM and virtualization at some point, when I have more time.

----------

## Vlad

Ahh I see, quite the complicated setup you have there.  Why not just roll all those FAT32 partitions into a single drive and have appropriately named folders?  I've had a few friends with (Windows) setups similar to yours, they create partitions for EVERYTHING - usually under the fall sense that having a different partition on the same drive somehow protects them from data loss. ;)  Thumbs up to keeping the /boot partition separate.

LVM is great, just confusing when you start using it...you might want to play with it a bit before you start putting any real data in it.  Whatever you decide, good luck!

----------

## wrc1944

During my windows days, I quickly got into the habit of having only the actually window OS on a relatively small C:\ partition, as invariably it would fill up and reach the point where defrag and scan disk would hardly function. Not to mention the almost mandatory every 6 month windows complete reinstall. I think most experienced windows users would say that having C:\ only host the OS, and having multiple partitions for other data is generally a good idea, not only for easy reinstall, but also OS performance. Very important for high-intensity computer work, like audio/video.

With a pro audio setup you have large numbers of different types of huge files in various stages of completion and editing. I like to keep each type/versions, such as Sonar project files, SoundForge/Audacity audio edits/versions of the same composition, and final master mixed .wav files on their own partitions, for easier house-keeping and backup to dvd disks.

Anyway, that's my current thinking on the subject.   :Wink: 

----------

## Vlad

Ah yes, I can totally relate to that.  Quit doing it after I needed to reinstall my applications most of the time due to missing registery entries and what not.  Never really bought into the idea that performance is better having the OS stuff on a separate partition, either; those files change pretty infrequently, so fragmentation of them isn't an issue, so their performance isn't likely to degrade (much).  Granted, if you're dicing up videos, you need loads of disk space and those large files are going to get fragmented, but then that happens regardless of where put them.

I suppose in the end it boils down to personal preferences.  If it helps you make backups, well...how could I possible argue with that! ;)

Oh, and if I might suggest something: when you start using LVM, you might want to write out a plan for what you're going to do.  The move from simple partitions to physical volumes, volume groups, and logical volumes can be a lot to handle.  Might also help to print out a log of what commands you used to do everything.  Might make disaster recovery (or installation of another distribution) a bit less painful.  Oh, and the Gentoo-Wiki would be a good read for when you do.

----------

