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Old 05-17-2011, 02:19 AM   #1
nivedhitha
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Significance of '8e'


From my little experience with LVM, my doubt is, what is the significance of selecting the partition filesystem of a PV as 8e?. Even if the partition filesystem is selected as 83 and made as PV, it still works fine when being made part of a VG and then all other LVM operations work fine.

Thank you.
 
Old 05-17-2011, 02:25 AM   #2
acid_kewpie
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Well whilst the LVM drivers have the "right" to only look for 83 type partitions it's hardly a lot more work to read the first few sectors of all partitions just in case it's wrong. Clearly you should still make them 8e and there's nothing positive in making it report as any other filesystem type at all.
 
Old 05-17-2011, 05:19 AM   #3
GazL
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My understanding is that the lvm subsystem/commands work at a block device level, and so don't see or care about the partition type themselves, but from a correctness standpoint it's an interesting question.

What if you have your PV on a luks encrypted partition. I always create mine as type 8e, but technically speaking the raw partition isn't a LVM PV, it's a luks container so type 8e isn't strictly speaking correct.

Does the existence of type 8e have any point at all?

Last edited by GazL; 05-17-2011 at 05:30 AM.
 
Old 05-17-2011, 06:03 AM   #4
syg00
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Apparently not. I had believed (hoped) the "destructive" tools (pvcreate, mkswap, mkfs ...) would check for an appropriate type before trashing the partition.
Wishful thinking.

A quick test shows they will all trash another type quite happily. The only query I got was when I did a pvcreate over the top of a swap partition - it recognised the swap header. Reply "y" and it goes right ahead - it ignores any type mismatch (as did mkswap).
Note: there was no equivalent query when I did a pvcreate over the top of an ext4 filesystem.
 
Old 05-18-2011, 01:17 AM   #5
nivedhitha
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Thank you all for your replies. So it seems that you need to select the correct partition filesystem type anyway - just to be on the safer side.

Thanks All!
 
  


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