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Bug 1368915 - Use two disks to create raid5 should be failed on cockpit,but it was successfully.
Summary: Use two disks to create raid5 should be failed on cockpit,but it was successf...
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: cockpit
Version: 7.2
Hardware: x86_64
OS: Linux
unspecified
medium
Target Milestone: pre-dev-freeze
: ---
Assignee: Marius Vollmer
QA Contact: qe-baseos-daemons
URL:
Whiteboard:
Depends On:
Blocks: ovirt-node-ng-platform
TreeView+ depends on / blocked
 
Reported: 2016-08-22 06:07 UTC by Yihui Zhao
Modified: 2016-09-20 14:21 UTC (History)
13 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-09-20 14:21:17 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
three_disks_raid5_success.png (57.48 KB, image/png)
2016-08-22 06:07 UTC, Yihui Zhao 		no flags Details
two_disks_raid5_failed.png (13.63 KB, image/png)
2016-08-22 06:08 UTC, Yihui Zhao 		no flags Details
two_disks_raid5_cockpit1.png (169.09 KB, image/png)
2016-08-22 06:09 UTC, Yihui Zhao 		no flags Details
two_disks_raid5_cockpit2.png (143.48 KB, image/png)
2016-08-22 06:09 UTC, Yihui Zhao 		no flags Details
ks file (1.75 KB, text/plain)
2016-08-22 06:10 UTC, Yihui Zhao 		no flags Details
View All

Description Yihui Zhao 2016-08-22 06:07:50 UTC 
Created attachment 1192772 [details]
three_disks_raid5_success.png

Description of problem:
Use two disks to create raid5 successfully on Cockpit about RHVH4.0.
But in fact,we can create raid5 with at least three disks.

Version-Release number of selected component (if applicable):
redhat-virtualization-host-4.0-20160817.0
cockpit-0.114-2.el7.x86_64
cockpit-ovirt-dashboard-0.10.6-1.3.6.el7ev.noarch

How reproducible:
100%

Steps to Reproduce:
1.Install NGN4.0
2.Run cockpit client in Firefox/chrome(ip:9090)
3.Switch to storage page
4.Create raid5 with two disks
5.For about twenty minutes,it is successful to create raid5.

Actual results:
Use two disks to create raid5 successfully on Cockpit about RHVH4.0.


Expected results:
Use two disks to create raid5 failed on Cockpit about RHVH4.0.
Also,we can create raid5 with at least three disks.For details,on attachment:
two_disks_riad5_cockpit1.png , two_disks_raid5_cockpit2.png , two_disks_raid5_failed.png, three_disks_raid5_success.png





Additional info:
My testing environment is using two 100G and clean iscsi disks to create raid5 successfully on cockpit.
Comment 1 Red Hat Bugzilla Rules Engine 2016-08-22 06:07:58 UTC 
Target release should be placed once a package build is known to fix a issue. Since this bug is not modified, the target version has been reset. Please use target milestone to plan a fix for a oVirt release.
Comment 2 Yihui Zhao 2016-08-22 06:08:54 UTC 
Created attachment 1192773 [details]
two_disks_raid5_failed.png
Comment 3 Yihui Zhao 2016-08-22 06:09:29 UTC 
Created attachment 1192774 [details]
two_disks_raid5_cockpit1.png
Comment 4 Yihui Zhao 2016-08-22 06:09:58 UTC 
Created attachment 1192775 [details]
two_disks_raid5_cockpit2.png
Comment 5 Yihui Zhao 2016-08-22 06:10:51 UTC 
Created attachment 1192776 [details]
ks file
Comment 6 Fabian Deutsch 2016-08-22 06:33:17 UTC 
Maybe this should even go to storaged ..
Comment 8 Marius Vollmer 2016-09-13 12:17:33 UTC 
The mdraid subsystem allows creating raid level 5 devices with only two disks.  

It might be a bad idea, but it can be done.  I think it treats it as a three-drive array where one drive has failed.

We might want to warn against this use, of course.  I'll ask around for more input.
Comment 9 Frank Ch. Eigler 2016-09-13 21:19:19 UTC 
> I think it treats it as a three-drive array where one drive has failed. 

When run manually:

# dd if=/dev/zero of=DISK2 bs=1048576 count=128
# dd if=/dev/zero of=DISK1 bs=1048576 count=128
# losetup DISK2
# losetup DISK1
# mdadm --create /dev/md/test -l 5 --raid-disks 2 /dev/loop0 /dev/loop1

results in a md with 128mb capacity, so a happy redundant raid5, basically equivalent to raid1 mirror.
Comment 10 Marius Vollmer 2016-09-20 14:21:17 UTC 
(In reply to Frank Ch. Eigler from comment #9)
> > I think it treats it as a three-drive array where one drive has failed. 
> 
> When run manually:
> 
> # dd if=/dev/zero of=DISK2 bs=1048576 count=128
> # dd if=/dev/zero of=DISK1 bs=1048576 count=128
> # losetup DISK2
> # losetup DISK1
> # mdadm --create /dev/md/test -l 5 --raid-disks 2 /dev/loop0 /dev/loop1
> 
> results in a md with 128mb capacity, so a happy redundant raid5, basically
> equivalent to raid1 mirror.

Thanks.  Let's keep this as a feature then.
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