Messages in this thread |  | | | Date | Fri, 24 Mar 2000 11:48:50 +0100 | | From | Helge Hafting <> | | Subject | Re: Fake SCSI devices |
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>>Machines connected in this fashion may also share scsi devices. The >>read-only cases are trivial, you must take grat care with anything writeable.
>Writeablity would be very desirable! How much does Digital sell their SCSI >hubs for?
You can share writeable stuff. The problem is software, not equipment. Basically, only one of the two (or more) machines can use a writeable partition at once.
So several machines may mount the same partition read-only (or the same cdrom) Only one can mount a partition for writing. Other partitions may still be read/written by other machines. The machines can take turns writing to a partition, but one must unmount before another gets it.
This because each machine have a disk cache, and can't know when the other is writing to the disk. Cache contents will be wrong after such a write. You probably can't snoop a scsi bus, and even that would be open to races.
If you want both to mount the same partition for writing (or one writing and another simultaneous read-only) please write a new filesystem where each machine ask all the others for permission (and invalidate their cached blocks) before each write.
Helge Hafting
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