[gpfsug-discuss] Experiences with thinly-provisioned volumes?

Marc A Kaplan makaplan at us.ibm.com
Tue Dec 22 22:44:08 GMT 2015


You write "storage device incorrectly reporting...".  Please give an 
example.  What numbers do you expect?  Why? What numbers are you seeing? 
Exactly because of what is highlighted in red "GPFS does not communicate 
block deallocation events...." -- I would not expect deleting files to 
change
"storage device  report [of]... usage allocations".   The device saw GPFS 
write to some data blocks and ... nothing after that ... so the device 
still "thinks" those blocks are in use.
Indeed GPFS may re-use/re-write those blocks in the future when they 
become part of another file"  OTOH GPFS may not do that until it has 
written to every other block that is addressable from its point of view. 
GPFS has no idea that the thin provisioning layer exists and might favor 
re-using one disk address over using another.

See also https://en.wikipedia.org/wiki/Trim_(computing)


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