Thanks Andreas,
Since it is possible, although rare to have two valid FIDs
map to the same inode, I'll keep that in mind ;)
Kris
On 1/31/15 12:21 AM, Dilger, Andreas wrote:
The similarity between FIDs and inode numbers is intentional, but FIDs are 128
bits (96 bits of you ignore the unused f_ver for now) while inode numbers are
only 64 bits (or 32 on 32-bit CPUs).
The mapping of FIDs to inode numbers will not overlap for a long time, but
eventually there would be duplicates if the filesystem is used long enough
and/or is very large (lots of MDTs and OSTs and clients).
The FIDs themselves will never be reused, so they will always be unique for
each file. The inode numbers are not strictly guaranteed to be unique, but due
to the long period between FIDs that map to the same inode, the chance of
64-bit inode number collisions is very small. The chance of collisions on
32-bit apps/CPUs is much higher, and guaranteed for large filesystems with more
than 4B inodes (though it would likely be hit earlier).
Cheers, Andreas
On Jan 30, 2015, at 16:25, Kristen J. Webb <[email protected]> wrote:
Here is my current lustre version for testing:
# cat /proc/fs/lustre/version
lustre: 2.6.92
kernel: patchless_client
I've noticed that my changelog records look a lot like generated inodes. From
a changelog entry:
[0x200000bd2:0x13a:0x0]
And from ls -i on a lustre client:
144115238843711802 (0x200000BD200013A)
This is nice, if I split the inode number into the sequence and oid numbers
(ignoring the version for now) I can use this in calls like
lfs fid2path
Will I always be able to do this with 64 bit inodes that I get with calls like
ls -i on a lustre client?
If not, then is it accurate to say that at any point in time, for each unique
file in a lustre file system, there is only one FID=[seq:oid:ver] that can be
used to generate a unique 64 bit inode for clients (even if the value of the
inode does not map backwards like the example above)?
Kris
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