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On Wed, 24 Nov 2010 01:10:02 +0100, Alan McKinnon wrote about Re: |
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[gentoo-user] Boot partitions (WAS: migrating disks (from mounts to |
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disklabels: |
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|
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>Apparently, though unproven, at 01:14 on Wednesday 24 November 2010, |
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>David W Noon did opine thusly: |
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> |
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>> >Errm, not exactly. SCSI/SATAs are limited to 15 (inc. one extended |
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>> >partition) and old (legacy driven) IDEs are limited to some 63 |
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>> >partitions if I recall correctly. If you use the new libata I think |
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>> >you only get 15 partitions for SATA/PATA. |
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>> |
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>> Well that's a software limitation. I am a little surprised that |
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>> the limit is so small, as Windows can support 24 drive letters |
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>> (C: through Z:) assigned to hard drive partitions. Of course, |
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>> accessing the CD-ROM would then be a bit sporty under Windows. |
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> |
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>Not quite, you are confused. |
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No, you should read again what I wrote. |
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>That's 24 'drives" of all kinds spread across all kinds: |
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> |
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>removeable media |
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>hard disks (all partitions) |
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>full disk (without partitions) |
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>network drives |
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>"$other_stuff" (a catchall for anything else MS might dream up). |
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> |
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>16 for SCSI is plenty in real life, and it's a hardware limitation not |
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>a software one so the driver can't be updated for this. |
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|
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The disk hardware knows nothing about partition tables. |
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|
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The partition table layout used on IA32 and AMD64 hardware is a |
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convention inherited from IBM's Industry Standard Architecture (ISA) |
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specification and the BIOS of the PC/AT (with revisions for the PS/2, |
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etc., plus extensions by Phoenix, AMI and Wang/Award). We still use |
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that under Linux, some 25+ years on. |
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|
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Other operating systems can use radically different partition table |
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layouts. Any disk partitioned that way -- whatever it is -- would be |
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unreadable by Linux, Windows, OS/2 or any other OS that uses ISA |
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assumptions. |
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|
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The SCSI/SATA/PATA hardware is totally agnostic about this, as it uses |
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absolute sector addresses, without any concept of partitioning, to |
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handle physical I/O requests. The sector address can be CHS (on older |
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disks) or LBA, but it *never* relates to a partition, only to a |
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complete disk. |
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>24 drive letters has *nothing* to do with partition number limits. |
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>They are not even vaguely related. |
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It seems you didn't get the joke. I probably should have put a "winky" |
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after the line ending "a bit sporty under Windows." |
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-- |
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Regards, |
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|
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Dave [RLU #314465] |
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dwnoon@××××××××.com (David W Noon) |
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