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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.
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.
Created attachment 1192773 [details] two_disks_raid5_failed.png
Created attachment 1192774 [details] two_disks_raid5_cockpit1.png
Created attachment 1192775 [details] two_disks_raid5_cockpit2.png
Created attachment 1192776 [details] ks file
Maybe this should even go to storaged ..
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.
> 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.
(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.