Date: Sat, 22 Sep 2012 09:50:49 +0530 From: Jack <jacks.1785@gmail.com> To: freebsd-geom@freebsd.org Subject: GEOM and CAM pass behaviour Message-ID: <CACmXQA2CiBJGZm836TUny48mnz0EYCj07E2=w9udT0ES1r8fpw@mail.gmail.com>
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Hi all, I would like to know 2 things regarding geom and cam pass driver behaviour. It would be helpful if someone could educate me regarding this. Consider the case where a scsi/ata tape/hard drive is attached to the system after the FreeBSD is booted(from different drive) completely. 1. Is it true that GEOM layer will always taste the (hard drive/tape drive)device whether we access device via cam pass driver or do block access. In other words, say if we never do a block access on the selected device, and we only access this device via cam pass driver, will then Geom will ever have to taste(e.g. for partition table, etc. or for other purposes) this device.? or is it something like, as soon as the device is attached, geom layer will always taste it - it doesn't matter how we access the device. 2. Also, is it possible that while a process is accessing the selected device via cam pass driver, the block access is also possible at that same time, (by same or different process) to that same device. I know that when a process is accessing the device via block access, it is possible for another(or even same) process to access that same device via cam pass driver, but I would like to know whether the other way is true also. Thanks. -- Jack
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