Bug 2095492
| Summary: | request for memory usage warning when setting up dm-writecache | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 8 | Reporter: | David Teigland <teigland> |
| Component: | lvm2 | Assignee: | David Teigland <teigland> |
| lvm2 sub component: | Cache Logical Volumes | QA Contact: | cluster-qe <cluster-qe> |
| Status: | CLOSED ERRATA | Docs Contact: | |
| Severity: | medium | ||
| Priority: | medium | CC: | agk, cluster-qe, cmarthal, djeffery, heinzm, jbrassow, jpittman, mcsontos, msnitzer, prajnoha, teigland, zkabelac |
| Version: | 8.0 | Keywords: | FutureFeature, Triaged |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | lvm2-2.03.14-4.el8 | Doc Type: | Enhancement |
| Doc Text: | Story Points: | --- | |
| Clone Of: | 2059644 | Environment: | |
| Last Closed: | 2022-11-08 10:55:29 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 2059644 | ||
| Bug Blocks: | |||
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Comment 3
David Teigland
2022-06-09 18:59:56 UTC
Marking verified in the latest rpms.
# RHEL8.7
kernel-4.18.0-398.g366e.el8.kpq1 BUILT: Tue Jun 7 04:56:38 CDT 2022
lvm2-2.03.14-4.el8 BUILT: Wed Jun 15 17:14:34 CDT 2022
lvm2-libs-2.03.14-4.el8 BUILT: Wed Jun 15 17:14:34 CDT 2022
dm-writecache memory usage
The amount of main system memory used by dm-writecache can be a factor when selecting the writecache cachevol size and the writecache block size.
· writecache block size 4096: each 100 GiB of writecache cachevol uses slighly over 2 GiB of system memory.
· writecache block size 512: each 100 GiB of writecache cachevol uses a little over 16 GiB of system memory.
[root@hayes-01 ~]# cat /proc/meminfo
MemTotal: 263626796 kB
[root@hayes-01 ~]# lvcreate --yes --type linear -n write -L 6T vdo_sanity
Logical volume "write" created.
[root@hayes-01 ~]# lvchange --yes -an vdo_sanity/write
[root@hayes-01 ~]# lvcreate --yes -L 4T -n wc_lv vdo_sanity
Logical volume "wc_lv" created.
[root@hayes-01 ~]# lvconvert --yes --type writecache --cachevol vdo_sanity/write vdo_sanity/wc_lv
Using writecache block size 4096 for unknown file system block size, logical block size 512, physical block size 512.
WARNING: unable to detect a file system block size on vdo_sanity/wc_lv
WARNING: using a writecache block size larger than the file system block size may corrupt the file system.
WARNING: writecache size 6.00 TiB will use 132 GiB of system memory (251 GiB).
Logical volume vdo_sanity/wc_lv now has writecache.
Verified in the latest kernel/lvm2 rpms as well. kernel-4.18.0-411.el8 BUILT: Wed Jul 20 18:42:42 CDT 2022 lvm2-2.03.14-5.el8 BUILT: Thu Jul 14 09:23:13 CDT 2022 lvm2-libs-2.03.14-5.el8 BUILT: Thu Jul 14 09:23:13 CDT 2022 [root@hayes-02 ~]# lvconvert --yes --type writecache --cachevol vdo_sanity/write vdo_sanity/wc_lv Using writecache block size 4096 for unknown file system block size, logical block size 512, physical block size 512. WARNING: unable to detect a file system block size on vdo_sanity/wc_lv WARNING: using a writecache block size larger than the file system block size may corrupt the file system. WARNING: writecache size 6.00 TiB will use 132 GiB of system memory (251 GiB). Logical volume vdo_sanity/wc_lv now has writecache. 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 (lvm2 bug fix and enhancement update), 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-2022:7792 |