Very slow Fedora 22 installation

[Roderick Johnstone]

Hi

I'm currently running a Fedora 22 kickstart install to one of our backup 
servers. Its been running for nearly a day now!

The root partition is on ext4 but there is a btrfs file system on top of 
md raid6 that holds our user backups. Each users' files are rsycned to 
the btrfs filesystem and then a snapshot made, so there are many 
thousands of snapshots.

Currently the install has been running for nearly a day (the main screen 
is full of dots). Behind the scenes the installer seems to be working 
its way through all the snapshots with messages like this in storage.log:

05:11:42,844 INFO blivet: hiding device existing 9.1 TiB btrfs snapshot 
home_xxx/20130423-000501 (59677) with existing btrfs filesystem
05:11:42,848 DEBUG blivet: existing RAID raid6 size == 9.1 TiB
05:11:42,852 DEBUG blivet: existing RAID raid6 size == 9.1 TiB
05:11:42,857 DEBUG blivet: 
BTRFSVolumeDevice.removeChild: kids: 32903 ; name: btrfs.133 ;
05:11:42,858 INFO blivet: removed btrfs snapshot 
home_xxx/20130423-000501 (id 59677) from device tree
05:11:42,858 DEBUG blivet: lvm filter: adding home_xxx/20130423-000501 
to the reject list
05:11:43,540 DEBUG blivet: existing RAID raid6 size == 9.1 TiB

In my kickstart file I have a (legacy) line which I use to make sure 
that there is no possibility of the install happening to the wrong device:
ignoredisk --only-use=/dev/disk/by-id/ata-ST380815AS_9RA8ZRZK

where ata-ST380815AS_9RA8ZRZK is the disk I want to install the 
operating system to.

Is it possible that this is whats causing the slowness?

I guess I could remove the ignoredisk line now since I use the by-id 
name to identify the disk to install to in the 'part' commands. I think 
we introduced 'ignoredisk' ages ago when we had to specify partitions by 
names like /dev/hda1 and I was caught out once when the disks were 
enumerated in a different order in the installer than in the previous 
operating system I was using and the install happened to the wrong device.

I'm disinclined to interrupt the install at the moment, as it does seem 
to be making progress, but confirmation that removing the 'ignoredisk' 
line would avoid the issue I described would be useful.

Thanks

Roderick Johnstone