Frank Golden Posted October 17, 2009 Share Posted October 17, 2009 Must not be a SATA drive. Can't have that many partitions with SATA. Eric, what is the limit and does it apply to Windows? Quote Link to comment Share on other sites More sharing options...
Bruno Posted October 18, 2009 Share Posted October 18, 2009 The max for sata drives is 15 . . . and yes that is for Windows too. Bruno Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 18, 2009 Share Posted October 18, 2009 I answered you, Frank, but the board dropped a bunch of posts from yesterday. Quote Link to comment Share on other sites More sharing options...
Frank Golden Posted October 19, 2009 Author Share Posted October 19, 2009 (edited) I answered you, Frank, but the board dropped a bunch of posts from yesterday. :">Yup, I know it Eric. I did some research and it seems that the 15 partition limit is a Linux issue.I can't find any reference to Windows having a similar limitation. At any rate if a person were to partition a satadrive with more than 15 partitions with Windows installed on one or more of them and linux distros, the linux distroswould be limited to seeing only the first 15 partitions, ignoring the rest.During my search I found this e-mail question/response "explaining" this.http://www.opensubscriber.com/message/fedo...om/5241705.htmlTom Horsley wrote: In an excess of energy I decided to see how many different OSes I could install to compare their behavior with a weird X bug I encountered in FC6: https://bugs.freedesktop.org/show_bug.cgi?id=8790 I figured 20 gig was about enough for each root, and decided to create 7 small /boot partitions near the front of the disk (since so many boot loaders have problems with big addresses) and 7 20 gig partitions after that for different kernels (my disk is a 160 gig sata drive). Windows has no problems doing this, but fdisk -l won't print any info about partitions after /dev/sda15 and if I try to install FC5 on a system that actually has an sda16 and sda17 partition (even if I don't try to use them for anything), anaconda blows up at the partitioning stage when it is about to try to partition and install. If I go back to windows, delete the last two partitions, and re-install, all goes smoothly. Is there some rule I don't know about on the number of partitions? Or is it a rule about the starting address of a partition (can't be too big maybe)?I don't know -- you seem to have worked it out pretty well for yourself.Linux can't cope with anything more than sdx15.This is basically because Linux's SATA support is based on its SCSIsupport, which means it inherits the SCSI device numbers. And the SCSIdevice numbers were designed for large computers, with lots ofrelatively small disks.As a result, the current device numbering (which goes back to thebeginning of Linux) allows for 128 disks, but only sixteen "minor"numbers per disk -- one for the whole disk, four for the primarypartitions, and eleven (sdx5 to sdx15) for logical partitions.The 2.6.x kernel in theory would support "larger" device numbers, whichcould allow for even more SCSI disks and more partitions per disk -- butthat would leave incompatibilities with stuff that expected old-styledevice numbers. Last I heard, the kernel team were planning to switchduring the 2.7.x development tree -- which shows how long ago that was.Since the plans for 2.7 were dropped, everything seems to have gonequiet. http://lwn.net/Articles/54837/ from 2003 is about the most recentstatus update I can find.Sorry.James Edited October 19, 2009 by Frank Golden Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 19, 2009 Share Posted October 19, 2009 ...if a person were to partition a satadrive with more than 15 partitions with Windows installed on one or more of them and linux distros, the linux distroswould be limited to seeing only the first 15 partitions, ignoring the rest.That is precisely (well, almost) the problem that I used to have with my previous system setup. I had an EIDE drive with 18 partitions. My Linux /swap was partition #18. If I installed any of the Linux distros using the libATA kernel drivers, I could not get them to see /swap because it was above #15 on the drive. In one instance, I corrected this by compiling my own kernel without libATA (in Zenwalk). This worked great! I remember reading somewhere that SATA drives were limited to 15 partitions PERIOD, regardless of OS. Unfortunately, I can't find any info like that doing a quick Google search. I'm interested in a definitive answer. Quote Link to comment Share on other sites More sharing options...
Frank Golden Posted October 20, 2009 Author Share Posted October 20, 2009 (edited) That is precisely (well, almost) the problem that I used to have with my previous system setup. I had an EIDE drive with 18 partitions. My Linux /swap was partition #18. If I installed any of the Linux distros using the libATA kernel drivers, I could not get them to see /swap because it was above #15 on the drive. In one instance, I corrected this by compiling my own kernel without libATA (in Zenwalk). This worked great! I remember reading somewhere that SATA drives were limited to 15 partitions PERIOD, regardless of OS. Unfortunately, I can't find any info like that doing a quick Google search. I'm interested in a definitive answer.Hi Eric, I don't know if this is definitive but I just created 19 partitions on a spare sata drive to check it out.I created a mix of NTFS, Fat 32, ext3 and a linux swap partition.On the first partition (NTFS) I installed Win 7 RC and on the ext3 partition I installed Ubuntu 8.10 64 bit.Windows was able to see and access 17 of the 19 partitions (the linux partitions being invisible of course).See the screenshot below of My Computer showing the 17 partitions.Ubuntu only shows 12 of the possible 15 partitions in Computer.I don't know why Ubuntu doesn't see all 15 but that is what it is.See screenshot below.I would think however that the practical limit in Windows would be the limited drive letters available (only the 26 letters in the english language).From my testing it appears that the 15 partition limit doesn't apply to Windows. Edited October 20, 2009 by Frank Golden Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 20, 2009 Share Posted October 20, 2009 Looks pretty darned definitive to me, Frank! Quote Link to comment Share on other sites More sharing options...
zlim Posted October 20, 2009 Share Posted October 20, 2009 I would think however that the practical limit in Windows would be the limited drive letters available (only the 26 letters in the english language). I'm almost positive I read somewhere that when the 26 English letters are used, then the designation is AA, BB, CC, etc. so another 26 are possible.Of course why anyone would need more than 26 partitions is beyond my comprehension. :hysterical:I can handle three on one computer and that's about my limit. More than that and it is too distracting and time consuming to be sure things are up to date.I'm up to 7 computers in the house - more than I really want and I will be somewhat thankful when MS drops support for windows 2000. Even though support was supposed to end July 2009, security/critical updates are still offered. I'll keep them online and updating until it ends. Then only 3 computers will need updating. Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 20, 2009 Share Posted October 20, 2009 ...why anyone would need more than 26 partitions is beyond my comprehension.BIG hard drive... LOTS of Linux distributions installed! Quote Link to comment Share on other sites More sharing options...
Bruno Posted October 20, 2009 Share Posted October 20, 2009 BIG hard drive... LOTS of Linux distributions installed! Run them in VirtualBox and you need less partitions and can run 100's distros if you likeB) Bruno Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 20, 2009 Share Posted October 20, 2009 Virtual Box is like virtual cake. I prefer the real thing. Quote Link to comment Share on other sites More sharing options...
securitybreach Posted October 20, 2009 Share Posted October 20, 2009 Frank Golden: All I can say is WOW!!!!Thanks Quote Link to comment Share on other sites More sharing options...
Frank Golden Posted October 21, 2009 Author Share Posted October 21, 2009 (edited) I'm almost positive I read somewhere that when the 26 English letters are used, then the designation is AA, BB, CC, etc. so another 26 are possible.From Wikipedia article about drive letters.http://en.wikipedia.org/wiki/Drive_letter_assignmentIt is not possible to have more than 26 mounted drives. If access to more filesystems than this is required, Volume Mount Points must be used.[6] However, it is possible to mount non-letter drives, such as 1:, 2:, or !: using the command line subst utility in Windows XP or Vista (i.e. "subst 1: c:\temp"), but this is not officially supported and may break programs that assume that all drive letters are A-Z.I have on my main 320 GB HDD 9 partitions. (4 linux distros, 1 linux swap, Win 7, XP pro, a large NTFS and a large Fat 32 partition) Actually linux sees this as 10 because it counts the extended partition that has 5 logical partitions as an extra partitionwhich in reality it is.I think that for now I'm happy with my present arrangement but I feel for Eric in his need to run many distros because the limitation affects him more than me.As for the impact of the my 9 partitions relative to drive letter assignments the 5 ext3 partitions are completly ignored by Windows. Edited October 21, 2009 by Frank Golden Quote Link to comment Share on other sites More sharing options...
Frank Golden Posted October 21, 2009 Author Share Posted October 21, 2009 The max for sata drives is 15 . . . and yes that is for Windows too. BrunoHi Bruno, doesn't apply to Windows. See the results of my testing posted later in this thread.17 partitions, all of them functional and accessible. Not counting the 1 ext3 and one Linux swap partitions that Windows can't see.That's 19 partitions.For some reason Ubuntu only sees 12. The swap makes 13 but of course it can't be mounted. Quote Link to comment Share on other sites More sharing options...
zlim Posted October 21, 2009 Share Posted October 21, 2009 Thanks Frank for digging to find the story. I had my "facts" mixed up again! Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 21, 2009 Share Posted October 21, 2009 Yes. Very informative, Frank. I wish we would have started a new thread with this topic, though. Maybe Bruno or someone could split these threads about the SATA stuff off to a new thread? Quote Link to comment Share on other sites More sharing options...
Bruno Posted October 21, 2009 Share Posted October 21, 2009 Maybe Bruno or someone could split these threads about the SATA stuff off to a new thread? Done !! Bruno Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 22, 2009 Share Posted October 22, 2009 Wow! What great service we get around here. Quote Link to comment Share on other sites More sharing options...
Peachy Posted October 22, 2009 Share Posted October 22, 2009 Late to the party, but yes, there are no restrictions to the number of partitions possible on a SATA drive other than the BIOS limitation of 4 primary partitions or 3 primary and 1 extended with no limit on the number of logical partitions (although I suspect with a 48-bit LBA system there must be some mathematical limit.) Windows using NTFS can handle more than 15 partitions and assign at least 26 drive letters while any extras can be dealt with using mount points.I suspect in Linux you could overcome the 15 partition limit using LVM, but I'd have to experiment with that. Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 22, 2009 Share Posted October 22, 2009 The limit in Linux is caused by the libATA kernel drivers. I've shown that you can compile your own kernel w/o libATA that will recognize partitions over the 15 limit. Bruno and I both shook our heads about the use of libATA in the current kernels when they first started using it back in 2.6.x in 2006 or so. I never have understood the advantages of libATA. I'm sure it's something to do with hal or udev. It's over my head, though. Quote Link to comment Share on other sites More sharing options...
mhbell Posted October 25, 2009 Share Posted October 25, 2009 Guess I will have to add my 02 cents worth. I use a 3rd party boot manager called boot-it-nt and can have up to 200 primary partitions on one drive if I so desire. below is the info. I have never tried it but maybe someone in the forum will someday. MelBootIt™ Next Generation Compatible with all Windows versions (9x/Me/NT/2000/XP/2003/Vista/2008/Win7/Servers) Compatible with x64 (AMD64/EM64T) and Windows 64bit OS (non-GPT) IEEE1394/USB 2.0 high-speed support for imaging/partitioning Support for large hard drives (2 TB) and partitions (1-2 TB) Non-destructive resizing and conversion for FAT/FAT32 Non-destructive resizing for NTFS Creation and (secure) deletion of partitions/volumes Undelete partitions/volumes FAT/FAT32 formatting Copying and moving of partitions/volumes Support for Linux Ext2/Ext3 and ReiserFS file systems Imaging (including directly to CD-R/RW or DVD+R/+RW/-R/-RW) Boot any partition on any hard drive (via BIOS) Booting from the CD/DVD drive (via BIOS) Boot multiple operating systems from a single partition Create over 200 primary partitions (if desired) User ID and password protection Free minor-level version upgrades And lots more! TeraByte Unlimited has been a leading innovator of advanced multi-boot software since the mid-1990s. Click to see a quick history of BootIt™ Quote Link to comment Share on other sites More sharing options...
V.T. Eric Layton Posted October 25, 2009 Share Posted October 25, 2009 Interesting, Mel. I thought that Max Primary Partition rule was inviolate. I guess not. COOL! Quote Link to comment Share on other sites More sharing options...
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