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Re: requirement to (re)format volumes when installing

On Dec 10, 2012, at 4:56 PM, Adam Williamson <awilliam redhat com> wrote:

> On Mon, 2012-12-10 at 14:43 -0700, Chris Murphy wrote:
>> 1. To properly install to hardware RAID 0, 10, 5, 6, I effectively
>> have to learn kickstart. I can properly create the volumes myself,
>> informing the file system at make time what the chunk and stripe width
>> are. The anaconda requirement to reformat in this case is
>> unreasonable.
> Um. What? Formatting the resulting 'disks' does not affect your
> configuration of the underlying RAID, as I understand it. The disks are
> logical representations of the RAID arrays you created. I don't see why
> it's a problem to format a partition that is backed by a hardware RAID
> array.

It's not a problem if you don't care to have an optimized file system for RAID.  If you do, it needs to be informed of the chunk and stripe size. Both XFS and ext4 have such options. If you just accept defaults you get an excessive read-write-modify penalty somewhere between "hmm" and "wow something is seriously wrong here." For software raid there is a discovery mechanism allowing the right options to be chosen at make file system time, that's not the usual case for hardware RAID.

RHEL 6 documentation says "Using proper stripe geometry greatly enhances performance of an ext4 file system."

I'll adjust the criticism somewhat: it's unreasonable to expect users to learn kickstart to have access to this optimization. Either the UI should give access to the option, or I should be allowed to do it myself with CLI tools without the installer blowing away that effort.

>> 3. The policy complicates the UI/UX of the Installation Destination
>> spoke. Both basic and advanced users can benefit from a simplified
>> point and shoot UI: select a pre-formatted volume, click an install
>> button. Two clicks and installation commences. This is  how 95% of the
>> world's desktop OS's work by default,
> <citation needed>

You'd like a citation for what, exactly? I've done roughly 100 Windows installs, and countless OS X installs. Combined they make up 95% of the desktop market. Neither of them require volume reformats to do installs, although both do check the file system to make sure it qualifies as a valid install target. OS X's installer doesn't even have a format option in it.

> you keep saying this, yet it doesn't accord with my understanding at
> all. No-one installs OS X from scratch, really, so forget about that.

I'm confused why you say no one installs OS X from scratch. Mac users have drives that die and need to be replaced, they have upgrade needs for faster or bigger drives. There is no such thing as buying drives from Apple with OS X pre-installed. Of course people install OS X from scratch. Really. And there isn't even an option to reformat in the installer.

> Windows is very keen on formatting disks, or at least was last time I
> checked it. You had to go into an advanced dialog to do anything other
> than let it have its way with an entire disk.

Not if it's already partitioned and formatted. Click on D: and it will install on D: so long as it's NTFS and meets whatever other requirements Microsoft has for the volume.

> From all my considerable
> experience, Linux distros generally let you do whatever you like in some
> way or other, and usually default to formatting an existing disk or
> using free space. I can't think of one which 'defaults' to re-using
> existing partitions.

Except when updating. So why is updating the OS exempt from the reformat?

Chris Murphy

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