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32bit dev_t

DISCUSSION Joel Becker 4 participants 5 messages Jan 21, 2003

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Joel Becker

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#0 lore raw

Folks,
Who is tracking the 32bit dev_t effort for 2.5? There are
already existing installations with 500 to 1000 disks attached to a system, and I don't know that Linux really wants to wait four years to get there!
If someone could point me to a current patch or any current
information about the issues, I'd really appreciate it.

Joel

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Joel Becker
Senior Member of Technical Staff
Oracle Corporation
E-mail: [email protected]
Phone: (650) 506-8127
#1 lore raw

Joel,

Linux doesn't really need a 32 bit kdev_t structure to support 1000 disks. There is plenty of device space available to support over 1500 disks by modifying the linux scsi layer.

Thanks
-steve

Quoted 12 lines · Joel Becker

Folks,
Who is tracking the 32bit dev_t effort for 2.5? There are
already existing installations with 500 to 1000 disks attached to a system, and I don't know that Linux really wants to wait four years to get there!
If someone could point me to a current patch or any current
information about the issues, I'd really appreciate it.

Joel

author
#2 lore raw
Quoted 3 lines · Steven Dake

Linux doesn't really need a 32 bit kdev_t structure to support 1000 disks. There is plenty of device space available to support over 1500 disks by modifying the linux scsi layer.

First, that's an approach that removes space from other devices.
In addition, I suspect we'll see 2000 disk systems before we see 2.8.

Joel

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Joel Becker
Senior Member of Technical Staff
Oracle Corporation
E-mail: [email protected]
Phone: (650) 506-8127
#3 lore raw
Quoted 7 lines · Joel Becker
Quoted 3 lines · Steven Dake

Linux doesn't really need a 32 bit kdev_t structure to support 1000 disks. There is plenty of device space available to support over 1500 disks by modifying the linux scsi layer.

First, that's an approach that removes space from other devices.
In addition, I suspect we'll see 2000 disk systems before we see 2.8.

Of course, we know the solution is /dev/disk, as mentioned by Linus at least a couple times, which eliminates a lot of dev_t limitation issues... :)

Jeff

#4 lore raw
In reply to Steven Dake
Quoted 5 lines · Steven Dake

Joel,

Linux doesn't really need a 32 bit kdev_t structure to support 1000 disks. There is plenty of device space available to support over 1500 disks by modifying the linux scsi layer.

You run out of assigned major/minor numbers. There is a sick hack that steals other device idents but thats not usable in a production environment. 32bit dev_t IMHO is essential to 2.6. Essential enough that if its not in the base 2.6 all the vendors have to get together and issue a Linus incompatible but common 32bit dev_t interface.