tomerlei
asked on
SCSI reserve/release commands
I need to know the details of the Reserve and Release scsi commands,
I mean, what exactly they do and how they do it?
And the same about persistent reserve/release command, for what they exist and what is the difference between persistent and the normal reserve/release?
I mean, what exactly they do and how they do it?
And the same about persistent reserve/release command, for what they exist and what is the difference between persistent and the normal reserve/release?
ASKER
what about the persistent reserve/release?
I'm pretty sure persistent reserve/release means "remember across resets". To reserve permanently until release even if power is disconnected. I expect most devices won't support this, unless they have some sort of storage. For example, a hard drive could easily support persistent reserve because it has storage, but, a dvd burner or printer probably won't support it because they usually don't have any non-volatile storage.
A hard drive used to boot the operating system would need persistent reserve because it is critical for it to have exclusive access for the boot process - boot would fail if someone else had it reserved. A printer would rarely need persistent reserve because it is a non-critical device - the OS doesn't require the printer for correct operation.
A hard drive used to boot the operating system would need persistent reserve because it is critical for it to have exclusive access for the boot process - boot would fail if someone else had it reserved. A printer would rarely need persistent reserve because it is a non-critical device - the OS doesn't require the printer for correct operation.
If you want to read the docs yourself, try the following search page:
http://www.t10.org/cgi-bin/search.cgi?PrevURL=%2Ft10docs.htm&PrevName=T10+Documents&Title=persistent&Author=&New=&Old=1994-001&Proto=&Revs=All&Maximum=10
http://www.t10.org/cgi-bin/search.cgi?PrevURL=%2Ft10docs.htm&PrevName=T10+Documents&Title=persistent&Author=&New=&Old=1994-001&Proto=&Revs=All&Maximum=10
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A short explanation:
SCSI allows devices to be shared on the SCSI bus - you could have multiple computers connected to a single SCSI chain. The reserve and release commands allow a computer to "own" a device and prevent other computers from affecting the device.
For example, say you had two pc's and a scsi burner all on the same scsi bus. One machine might "reserve" the burner device so the other computer won't mess up the burning process.