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Description of problem:
lvconvert does not change the read_ahead to zero after executing "lvconvert --thinpool vg/pool -r none"
"lvchange -r none" works well
Version-Release number of selected component (if applicable):
lvm2-2.02.99-1.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1.
2.
3.
[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
LV Rahead
pool auto
[root@dhcp12-156 tc]# lvconvert --thinpool vg/pool -r none
Logical volume "pool_tmeta" created
Logical volume "lvol0" created
Converted vg/pool to thin pool.
[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
LV Rahead
pool auto
[root@dhcp12-156 tc]# lvchange -r none vg/pool
Logical volume "pool" changed.
[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
LV Rahead
pool 0
[root@dhcp12-156 tc]# ls -l /dev/mapper/vg-pool
lrwxrwxrwx. 1 root root 7 Aug 7 07:17 /dev/mapper/vg-pool -> ../dm-5
[root@dhcp12-156 tc]# cat /sys/block/dm-5/queue/read_ahead_kb
0
Actual results:
Expected results:
Additional info:
This request was resolved in Red Hat Enterprise Linux 7.0.
Contact your manager or support representative in case you have further questions about the request.
The comment above is incorrect. The correct version is bellow.
I'm sorry for any inconvenience.
---------------------------------------------------------------
This request was NOT resolved in Red Hat Enterprise Linux 7.0.
Contact your manager or support representative in case you need
to escalate this bug.
There is currently no meaning behind read-ahead setting for thin-pool.
So before this BZ is fixed we need to check how to deal with this setting in kernel driver first.
Comment 10Jonathan Earl Brassow
2015-07-22 13:24:14 UTC
This bug will not be resolved for 7.2. The read-ahead setting for thin-pools makes no sense really, and this bug may simply be CLOSED NOTABUG.
However, there may be some utility in setting read-ahead for a pool, in that thinLVs might inherit the setting from the pool. (Although, that is better suited to an LVM config setting probably.) I'll leave this open for a while for some discussion.
Comment 12Jonathan Earl Brassow
2016-01-18 18:03:43 UTC
*** Bug 1006025 has been marked as a duplicate of this bug. ***
Comment 13Jonathan Earl Brassow
2016-01-18 18:06:27 UTC
There is not determination as to what read-ahead should mean for thin-pools and no discussion to resolve it. I'm closing this bug WONTFIX. It can be reopened if it is determined that this is a problem. (See comment 7 and comment 10 for reference.)