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Bug 1511871 - vdoformat has no limit for physical size if physical size is over 256T
Summary: vdoformat has no limit for physical size if physical size is over 256T
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: vdo
Version: 7.5
Hardware: Unspecified
OS: Unspecified
Target Milestone: rc
: ---
Assignee: John Wiele
QA Contact: Jakub Krysl
Depends On:
TreeView+ depends on / blocked
Reported: 2017-11-10 10:35 UTC by Jakub Krysl
Modified: 2019-03-27 00:15 UTC (History)
8 users (show)

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Description Jakub Krysl 2017-11-10 10:35:12 UTC
Description of problem:
I tried creating VDO on top of VDO with maximum allowed logical size 4P. because of this the upper VDO thinks physical size is actually 4P and fails with error:
vdo: ERROR - vdoformat: vdo.c:507: handleAssertionFailure: Assertion `config->physicalBlocks <= MAXIMUM_PHYSICAL_BLOCKS' failed.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. vdo create --device DEVICE --name VDO --vdoLogicalSize 4P
2. vdo create --device /dev/mapper/VDO --name VDO2

Actual results:
vdo: ERROR - vdoformat: vdo.c:507: handleAssertionFailure: Assertion `config->physicalBlocks <= MAXIMUM_PHYSICAL_BLOCKS' failed.

Expected results:
Actually not sure, maybe create VDO on only part of the block device and leaving the rest free. Or output error that the underlaying block device is too large, max size 256T.

Additional info:

Comment 2 Dennis Keefe 2017-11-10 13:38:52 UTC
Physical volumes larger than 256TB are not supported.  User should resize the volume to a smaller size otherwise the user might believe that there is additional available blocks to use or grow into.

Comment 3 Louis Imershein 2017-11-10 18:03:59 UTC
What's the practical use case for the behavior being suggested?

Comment 4 Jakub Krysl 2017-11-14 10:38:35 UTC
I cannot think of practical usage of VDO over VDO, but the bug this is hitting is not limited to just VDO over VDO. Wherever user tries to create VDO over storage larger than 256TB, this error should appear. (correct me if I am wrong)

So the most practical usage case I can think of would be creating VDO over array larger than 256TB. As VDO does not support sizes larger than 256TB, I suggest fixing this by giving the user exactly this information right away instead of uncaught error. This way user can split the storage however he likes.

Comment 5 bjohnsto 2017-11-14 18:40:56 UTC
This seems like something vdoFormat could check and provide a better error message for.

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