64-bit SCSI LUN addressing on Linux
Does Linux support 64-bit SCSI LUN addressing? Suppose I have a system that can create SCSI LUNs that are greater than 2TB using a block size of 512 bytes and can accept 16 byte CDBs, can I use this LUN with a 2.6 series Linux kernel?
If so, are there any filesystems (ext3, XFS, etc. ) that can use a LUN > 2TB?
Would I need any additional tools?
Would I need a 64-bit platform?
Quoted 4 lines · Martin W. Schlining III
Does Linux support 64-bit SCSI LUN addressing? Suppose I have a system that can create SCSI LUNs that are greater than 2TB using a block size of 512 bytes and can accept 16 byte CDBs, can I use this LUN with a 2.6 series Linux kernel?
Yes.
Quoted 2 lines
If so, are there any filesystems (ext3, XFS, etc. ) that can use a LUN > 2TB?
XFS has been tested heavily with big luns, but the others should work aswell.
Quoted 1 line
Would I need any additional tools?
no.
Quoted 1 line
Would I need a 64-bit platform?
For filesystem sizes < 16TB you can use 32bit platforms, above that you need a 64bit kernel.
Quoted 1 line · Martin W. Schlining III
Does Linux support 64-bit SCSI LUN addressing?
No. Linux supports 32 bit LUNs.
Quoted 1 line
Suppose I have a system that can create SCSI LUNs that are greater than 2TB using a block size of 512 bytes and can accept 16 byte CDBs, can I use this LUN with a 2.6 series Linux kernel?
There is no relationship between 64 bit LUNS (which, for example, support a hierarchy of up to 4, 16 bit LUNs) and the ability of a logical unit (LU) (e.g. a disk) to support 64 bit logical block addressing (LBA).
Christoph's reply more accurately addresses the question I think you were trying to ask...
In your title perhaps you could: s/LUN addressing/LBAs/ LUNs are about device addressing; LBAs are about block (or sector) addressing on a block device.
Doug Gilbert
Quoted 10 lines · Douglas Gilbert
Quoted 1 line · Martin W. Schlining III
Does Linux support 64-bit SCSI LUN addressing?
No. Linux supports 32 bit LUNs.
Quoted 4 lines
Suppose I have a system
that can create SCSI LUNs that are greater than 2TB using a block size of 512 bytes and can accept 16 byte CDBs, can I use this LUN with a 2.6 series Linux kernel?
Quoted 7 lines
There is no relationship between 64 bit LUNS (which, for example, support a hierarchy of up to 4, 16 bit LUNs) and the ability of a logical unit (LU) (e.g. a disk) to support 64 bit logical block addressing (LBA).
Christoph's reply more accurately addresses the question I think you were trying to ask...
Yeah, people tend to say LUNs when they mean storage devices a lot, so I've started to look over the slight misuses if things make sense otherwise.
Quoted 3 lines
Yeah, people tend to say LUNs when they mean storage devices a lot, so I've started to look over the slight misuses if things make sense otherwise.
We all have to do that, because the vast majority of people who are not storage engineers, and a disturbing portion of people who are, mean LU (or storage device) when they say LUN. But we shouldn't compound the problem by not pointing out the mistakes; people deserve to know there's a clearer way to say what they're trying to say. In many contexts, I have been genuinely confused as to whether a person was talking about a LUN or a LU. "LUN discovery," for example is a much simpler problem than the more general problem of LU (or volume or device) discovery. I end up having to do a meta-analysis of which language the author is most likely to be speaking. In the current discussion, we have the phrase "64-bit SCSI LUN addressing," which does sound a whole lot like it's about 64 bit LUNs. Only when you look closely do you see that decoded the other way, it makes more sense.
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Bryan Henderson IBM Almaden Research Center
San Jose CA Filesystems