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lvcreate: reject '--nosync' option for RAID6 LVs

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The MD raid6 personality being used to drive lvm raid6 LVs does
read-modify-write updates to any stripes and thus relies on correct
P and Q Syndromes being written during initial synchronization or
it may fail reconstructing proper user data in case of SubLVs failing.

We may not allow the '--nosync' option on
creation of raid6 LVs for that reason.

Update/fix 'man lvcreate' in that regard.

add lvcreate-raid-nosync.sh test script.

- Resolves rhbz1358532
This commit is contained in:
Heinz Mauelshagen 2016-08-08 13:52:35 +02:00
parent 57fa5d4329
commit 7d6cf12554
3 changed files with 112 additions and 7 deletions
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29
man/lvcreate.8.in
View File

@ -381,10 +381,11 @@ would result in a mirror with two-sides; that is,
a linear volume plus one copy.
Specifying the optional argument \fB\-\-nosync\fP will cause the creation
of the mirror to skip the initial resynchronization. Any data written
afterwards will be mirrored, but the original contents will not be
copied. This is useful for skipping a potentially long and resource
intensive initial sync of an empty device.
of the mirror LV to skip the initial resynchronization. Any data written
afterwards will be mirrored, but the original contents will not be copied.
This is useful for skipping a potentially long and resource intensive initial
sync of an empty mirrored RaidLV.
There are two implementations of mirroring which can be used and correspond
to the "\fIraid1\fP" and "\fImirror\fP" segment types.
@ -440,7 +441,21 @@ Without this option a default name of "lvol#" will be generated where
.HP
.BR \-\-nosync
.br
Causes the creation of the mirror to skip the initial resynchronization.
Causes the creation of mirror, raid1, raid4, raid5 and raid10 to skip the
initial resynchronization. In case of mirror, raid1 and raid10, any data
written afterwards will be mirrored, but the original contents will not be
copied. In case of raid4 and raid5, no parity blocks will be written,
though any data written afterwards will cause parity blocks to be stored.
.br
This is useful for skipping a potentially long and resource intensive initial
sync of an empty mirror/raid1/raid4/raid5 and raid10 LV.
.br
This option is not valid for raid6, because raid6 relies on proper parity
(P and Q Syndromes) being created during initial synchronization in order
to reconstruct proper user date in case of device failures.
raid0 and raid0_meta don't provide any data copies or parity support
and thus don't support initial resynchronization.
.
.HP
.BR \-\-noudevsync
@ -621,12 +636,14 @@ to the command.
.br
Note the current limitation of 8 stripes total in any RaidLV including parity devices.
See the \fB\-\-nosync\fP option to optionally avoid initial syncrhonization of RaidLVs.
Two implementations of basic striping are available in the kernel.
The original device-mapper implementation is the default and should
normally be used. The alternative implementation using MD, available
since version 1.7 of the RAID device-mapper kernel target (kernel
version 4.2) is provided to facilitate the development of new RAID
features. It may be accessed with \fB--type raid0\fP, but is best
features. It may be accessed with \fB--type raid0[_meta]\fP, but is best
avoided at present because of assorted restrictions on resizing and converting
such devices.
.HP

85
test/shell/lvcreate-raid-nosync.sh Normal file
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@ -0,0 +1,85 @@
#!/bin/sh
# Copyright (C) 2016 Red Hat, Inc. All rights reserved.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions
# of the GNU General Public License v.2.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
SKIP_WITH_LVMLOCKD=1
SKIP_WITH_LVMPOLLD=1
. lib/inittest
aux have_raid 1 7 0 || skip
aux prepare_vg 6
# Delay 1st leg so that rebuilding status characters
# can be read before resync finished too quick.
aux delay_dev "$dev1" 0 1
# raid0/raid0_meta don't support resynchronization
for r in raid0 raid0_meta
do
lvcreate --yes --type raid0 -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "AAA"
lvremove --yes $vg/$lv1
done
# raid1 supports resynchronization
lvcreate --yes --type raid1 -m 2 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "aaa"
aux wait_for_sync $vg $lv1
aux check_status_chars $vg $lv1 "AAA"
lvremove --yes $vg/$lv1
# raid1 supports --nosync
lvcreate --yes --type raid1 --nosync -m 2 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "AAA"
lvremove --yes $vg/$lv1
for r in raid4 raid5
do
# raid4/5 support resynchronization
lvcreate --yes --type $r -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "aaaa"
aux wait_for_sync $vg $lv1
aux check_status_chars $vg $lv1 "AAAA"
lvremove --yes $vg/$lv1
# raid4/5 support --nosync
lvcreate --yes --type $r --nosync -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "AAAA"
lvremove --yes $vg/$lv1
done
# raid6 supports resynchronization
lvcreate --yes --type raid6 -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "aaaaa"
aux wait_for_sync $vg $lv1
aux check_status_chars $vg $lv1 "AAAAA"
lvremove --yes $vg/$lv1
# raid6 rejects --nosync; it has to initialize P- and Q-Syndromes
not lvcreate --yes --type raid6 --nosync -i 3 -l 1 -n $lv1 $vg
# raid10 supports resynchronization
lvcreate --yes --type raid10 -m 1 -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "aaaaaa"
aux wait_for_sync $vg $lv1
aux check_status_chars $vg $lv1 "AAAAAA"
aux wait_for_sync $vg $lv1
lvremove --yes $vg/$lv1
# raid10 supports --nosync
lvcreate --yes --type raid10 --nosync -m 1 -i 3 -l 1 -n $lv1 $vg
aux check_status_chars $vg $lv1 "AAAAAA"
aux wait_for_sync $vg $lv1
lvremove --yes $vg/$lv1
vgremove -ff $vg

5
tools/lvcreate.c
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@ -562,7 +562,10 @@ static int _read_mirror_and_raid_params(struct cmd_context *cmd,
return 0;
}
lp->nosync = arg_is_set(cmd, nosync_ARG);
if ((lp->nosync = arg_is_set(cmd, nosync_ARG)) && seg_is_any_raid6(lp)) {
log_error("nosync option prohibited on RAID6");
return 0;
}
if (!(lp->region_size = arg_uint_value(cmd, regionsize_ARG, 0)) &&
((lp->region_size = get_default_region_size(cmd)) <= 0)) {