Messages in this thread | | | From | David Lang <> | Date | Thu, 3 Apr 2003 02:09:48 -0800 (PST) | Subject | Re: 64-bit kdev_t - just for playing |
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when you think of huge raid arrays that present themselves to the system as a single drive even 64 partitions can be limiting.
I don't really know what an appropriate limit would be, this may be something that has a default setting for static dev entries and they dynamic assignments can get more
David Lang
On 2 Apr 2003, H. Peter Anvin wrote:
> Date: 2 Apr 2003 14:03:58 -0800 > From: H. Peter Anvin <hpa@zytor.com> > To: linux-kernel@vger.kernel.org > Subject: Re: 64-bit kdev_t - just for playing > > Followup to: <200304020931.38671.pbadari@us.ibm.com> > By author: Badari Pulavarty <pbadari@us.ibm.com> > In newsgroup: linux.dev.kernel > > > > Roman, > > > > Here is the patch for sd to allow more than 256 disks. > > There are few issues with the patch that need to be resolved. > > > > 1) With the patch I get 16 bits for minor. Since 4 bits are used for > > partition, we get 12 bits to represent disks. So each major can support > > 2^12 =3D 4096 disks. Disks 0 - 4095 are mapped to major=3D8,=20 > > disks 4096 - 8191 to major =3D 65 and so on.. > > > > This means .. > > > > (i) I need to create nodes in /dev/ to match new <major, minor> for=20 > > these disks. Currently "mknod" is broken due to glibc issues with dev_t. > > > > (ii) We need to worry about backward compatibility. For example: > > 17th disk used to have <65, 0>. Now its major, minor is <8, 256>. > > So /dev/ entires need to be re-created to match these, everytime > > you reboot 2.4/2.5 etc. Greg KH udev might fix this for us.=20 > > > > 2) Do we still need 16 majors for disks ? > > > > No, we don't. On the other hand, we really should change to 64 > partitions/disk, same as for non-SCSI disks. 16 really is too small. > > -hpa > > -- > <hpa@transmeta.com> at work, <hpa@zytor.com> in private! > "Unix gives you enough rope to shoot yourself in the foot." > Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64 > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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