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Description of problem:
There is no warning when user fills vdo with data, instead he gets I/O errors right away. For comparison and inspiration this is how dm-thin handles this:
/var/log/messages:
[81469.069613] device-mapper: thin: 253:4: reached low water mark for data device: sending event.
This is mainly useful for thin provisioning as it gets admin enough time to increase physical size of the storage.
Version-Release number of selected component (if applicable):
kmod-kvdo-6.1.0.55-10
How reproducible:
100%
Steps to Reproduce:
1. create vdo
2. fill it with enough data to fill whole real physical size of VDO
Tested with kmod-kvdo-6.1.1.125-5.el7.x86_64 using 6G VDO on 10G drive. Filling VDO with dd oflag=direct, /var/log/messages:
Oct 2 17:13:39 storageqe-75 kernel: kvdo1:packerQ: compression is enabled
Oct 2 17:13:39 storageqe-75 UDS/vdodmeventd[14034]: INFO (vdodmeventd/14034) VDO device vdo is now registered with dmeventd for monitoring
Oct 2 17:13:39 storageqe-75 lvm[13863]: Monitoring VDO pool vdo.
Oct 2 17:27:39 storageqe-75 lvm[13863]: WARNING: VDO pool vdo is now 80.69% full.
Oct 2 17:28:19 storageqe-75 lvm[13863]: WARNING: VDO pool vdo is now 85.25% full.
Oct 2 17:29:39 storageqe-75 lvm[13863]: WARNING: VDO pool vdo is now 90.64% full.
Oct 2 17:30:29 storageqe-75 lvm[13863]: WARNING: VDO pool vdo is now 96.07% full.
For comparison this is what LVM thinp does in the exactly same situtation (6G physical):
Oct 3 09:33:05 storageqe-75 kernel: device-mapper: thin: Data device (dm-2) discard unsupported: Disabling discard passdown.
Oct 3 09:33:05 storageqe-75 lvm[13863]: Monitoring thin pool vg-tpool-tpool.
Oct 3 09:35:05 storageqe-75 lvm[13863]: WARNING: Thin pool vg-tpool-tpool data is now 87.32% full.
Oct 3 09:35:15 storageqe-75 lvm[13863]: WARNING: Thin pool vg-tpool-tpool data is now 97.76% full.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2018:3094