CentOS - Feb 2015 - CentOS 7: software RAID 5 array with 4 disks and no spares?

Le 18/02/2015 23:12, Chris Murphy a ?crit :
> What is NOT obvious: for single device installs, if you omit the size
> in the create mount point dialog, the size of the resulting volume
> will consume all remaining space. But since there's no way to preset
> raid5 at the time a mount point is created (raid5 is set after the
> fact), there isn't a clear way to say "use all remaining space for
> this". There's just a size field for the volume, and a space
available
> value in the lower left hand corner.
Well, maybe it's just me. I've started Linux on Slackware 7.1 and used 
pretty much every major and minor distribution under the sun. I know my 
way around Slackware, Debian, CentOS, FreeBSD, Gentoo, Arch and many 
more, and my favourite installer is - and will always be - Slackware's 
bone-headed NCurses installer that lets the admin do pretty much what he 
wants - and needs - to do. CentOS 5.x's text mode installer got pretty 
close, but then, for mysterious reasons, Red Hat decided to cripple it 
into oblivion. Go figure.

I love CentOS, been using it since 4.x. But frankly, CentOS 7's 
installer is an abomination.

All's well that ends well. It only took me a day and a half to figure 
out how to configure RAID 5 using the graphical assistant. Something I 
could have done in less than three minutes using fdisk and mdadm --create.

Cheers,

Niki

-- 
Microlinux - Solutions informatiques 100% Linux et logiciels libres
7, place de l'?glise - 30730 Montpezat
Web  : http://www.microlinux.fr
Mail : info at microlinux.fr
T?l. : 04 66 63 10 32

Niki Kovacs wrote:
> Le 18/02/2015 23:12, Chris Murphy a ?crit :
>> What is NOT obvious: for single device installs, if you omit the size
>> in the create mount point dialog, the size of the resulting volume
>> will consume all remaining space. But since there's no way to
preset
>> raid5 at the time a mount point is created (raid5 is set after the
>> fact), there isn't a clear way to say "use all remaining space
for
>> this". There's just a size field for the volume, and a space
available
>> value in the lower left hand corner.
<snip>
> close, but then, for mysterious reasons, Red Hat decided to cripple it
> into oblivion. Go figure.
One word: desktop. That's what they want to conquer
next.
>
> I love CentOS, been using it since 4.x. But frankly, CentOS 7's
> installer is an abomination.
>
> All's well that ends well. It only took me a day and a half to figure
> out how to configure RAID 5 using the graphical assistant. Something I
> could have done in less than three minutes using fdisk and mdadm --create.
We don't want to use lvm - my manager doesn't like it, and given how
much
we hit our machines, we almost don't use vm's, either - we need all CPU
cycles for some things (like heavy scientific computing).

We also pretty much don't use any drives under 1TB. The upshot is we had
custom scripts for > 500GB, which made 4 partitions - /boot (1G, to fit
with the preupgrade), swap (2G), / (497G - and we're considering
downsizing that to 250G, or maybe 150G) and the rest in another partition
for users' data and programs. The installer absolutely does *not* want to
do what we want. We want swap - 2G - as the *second* partition. But if we
use the installer, as soon as we create the third partition, of 497GB, for
/, it immediately reorders them, so that / is second.

Duh....

The result is that we get to the screen to choose the drive, and say
"custom partition"... then <alt-F2>, and use parted to make the
partitions, then go back to the GUI and just assign the mount points and
filesystem types.

And why would you *want* / to have everything? I want to be able to
install a newer o/s, or whatever, and not have to worry about all the
data, etc - I want that in a separate partition (no, don't format that,
thank you).

       mark

On Wed, Feb 18, 2015 at 3:59 PM, Niki Kovacs <info at microlinux.fr>
wrote:
> Well, maybe it's just me. I've started Linux on Slackware 7.1 and
used
> pretty much every major and minor distribution under the sun. I know my way
> around Slackware, Debian, CentOS, FreeBSD, Gentoo, Arch and many more, and
> my favourite installer is - and will always be - Slackware's
bone-headed
> NCurses installer that lets the admin do pretty much what he wants - and
> needs - to do.
I'm definitely not suggesting it's just you. I'm coming up with a
plausible explanation for the confusion, and that's a misalignment
between your expectations and the installer's presentation. I can tell
you, having using this installer since Fedora 18, it has changed
immensely from the initial versions.

My personal view on installers is extremely biased toward the user
staying out of trouble, they shouldn't have to read documentation for
a GUI installer. The entire point of a GUI installer is to protect the
user from bad choices, non-standard or unsupportable choices, or
having to read a volume of documentation, or become an expert for
something that quite frankly happens rarely: OS installation.

And my very strong bias is affected by both the OS X and Windows
installers, which are completely, utterly, brain dead. And I mean that
in a good way. It's impossible for the user to get confused, there are
almost no choices. It's next to impossible for there to be bugs, there
are almost no choices. Every outcome of the installation is
supportable, because the user wasn't allowed to create completely
nutty layouts that make no sense.

Now, for various reasons Anaconda (the Fedora/RHEL/CentOS installer)
is exceptionally more capable than almost any other GUI installer out
there. And that makes it complex, prone to bugs, and prone to
confusing users and subject to criticism. That's just the inevitable
result of trying to do so many things.


> I love CentOS, been using it since 4.x. But frankly, CentOS 7's
installer is
> an abomination.
Having done many hundreds, possibly over a thousand installations with
it, I'm well aware of how confusing it can be. So the criticism is
almost certainly reasonable, no matter what. I'm just saying that once
you understand the point of view of the installer (which arguably you
should not have to do), things become much easier. That doesn't mean
easy. Just easier.

> All's well that ends well. It only took me a day and a half to figure
out
> how to configure RAID 5 using the graphical assistant. Something I could
> have done in less than three minutes using fdisk and mdadm --create.
Right, but inevitably that failure is the result of misalignment of
expectations between you and the installer. That's an explanation, not
an assignment of blame. The reason why working directly with
partitions is easy for you, and what you expect, is simply because
that's how you've always done it, since  that's how all other
installers behave. Anaconda is really the first installer that
deemphasizes that. And I think that's a bold move, and for a GUI
installer that's necessarily taking on a lot of complexity I think
it's probably a good idea overall. But it does have a lot of bugs
still... it's definitely doing things that I don't like.

But any experienced sysadmin knows how users say "it should work like
X" and how often they're wrong. They're just used to things that
work
like X and that's why they want this new problem to work that same
way. So as a sysadmin or network engineer you ask questions to find
out how to get the user from A to B, and the details of "how it should
work" are your domain, your specialty, and ultimately they don't
really care how it happens, they just want to get to B. And once
that's well understood, you can get on with things.

And one problem is the installer can't really have that kind of
diplomatic conversation about what its worldview is, so that the user
expectations re-align with the end goal in mind, not how to get there.

-- 
Chris Murphy

On Wed, Feb 18, 2015 at 4:20 PM,  <m.roth at 5-cent.us>
wrote:
> Niki Kovacs wrote:
>> Le 18/02/2015 23:12,
>> close, but then, for mysterious reasons, Red Hat decided to cripple it
>> into oblivion. Go figure.
>
> One word: desktop. That's what they want to conquer next.
OK well there's a really long road to get to that pie in the sky. I
don't see it happening because it seems there's no mandate to
basically tell people what they can't have, instead it's well, we'll
have a little of everything.

Desktop OS that are the conquerers now? Their installers don't offer
100's of layout choices. They offer 1-2, and they always work rock
solid, no crashing, no user confusion, essentially zero bugs. The code
is brain dead simple, and that results in stability.

*shrug*

Long road. Long long long. Tunnel. No light. The usability aspects are
simply not taken seriously by the OS's as a whole. It's only taken
seriously by DE's and they get loads of crap for every change they
want to make. Until there's a willingness to look at 16 packages as a
whole rather than 1 package at a time, desktop linux has no chance.
The very basic aspects of how to partition, assemble, and boot and
linux distro aren't even agreed upon. Fedora n+1 has problems
installing after Fedora n. And it's practically a sport for each
distro to step on an existing distros installer. This is
technologically solved, just no one seems to care to actually
implement something more polite.

OS X? It partitions itself, formats a volume, sets the type code,
writes some code into NVRAM, in order to make the reboot automatically
boot the Windows installer from a USB stick. It goes out of it's way
to invite the foreign OS.

We can't even do that with the same distro, different version. It
should be embarrassing but no one really cares enough to change it.
It's thankless work in the realm of polish. But a huge amount of
success for a desktop OS comes from polish.

> We also pretty much don't use any drives under 1TB. The upshot is we
had
> custom scripts for > 500GB, which made 4 partitions - /boot (1G, to fit
> with the preupgrade), swap (2G), / (497G - and we're considering
> downsizing that to 250G, or maybe 150G) and the rest in another partition
> for users' data and programs. The installer absolutely does *not* want
to
> do what we want. We want swap - 2G - as the *second* partition. But if we
> use the installer, as soon as we create the third partition, of 497GB, for
> /, it immediately reorders them, so that / is second.
I'm open to having my mind changed on this, but I'm not actually
understanding why it needs to be in the 2nd slot, other than you want
it there, which actually isn't a good enough reason. If there's a good
reason for it to be in X slot always, for everyone, including
anticipating future use, then that's a feature request and it ought to
get fixed. But if it's a specific use case, well yeah you get to
pre-partition and then install.

-- 
Chris Murphy

Le 19/02/2015 05:43, Chris Murphy a ?crit :
> My personal view on installers is extremely biased toward the user
> staying out of trouble, they shouldn't have to read documentation for
> a GUI installer.
A *user* never has to even see - or use - an installer. A USER has to 
USE a computer,  by which I mean the applications he or she needs to get 
some work done.

The person who gets to be confronted by an OS installer is not a user, 
it's an ADMIN, which is an entirely different thing. An ADMIN should 
RTFM (a lot) and know his way about what you call "esoteric things" 
earlier in this thread (disks, partitions, volumes).

My company (http://www.microlinux.fr) installs complete Linux-based 
networks for schools, town halls, public libraries etc. here in South 
France. For now, most of my server and desktop solutions are based on a 
highly modified version of Slackware Linux, with some CentOS and some 
RHEL here and there. I'm currently planning on migrating everything to 
CentOS in the long run.

One of the founding principles of my company is the constant SEPARATION 
BETWEEN USING A COMPUTER AND ADMINISTRATING IT. A user never ever has to 
worry about things that pertain to system administration, and it would 
be very wrong if he or she ever has to deal with such a thing as an 
installer. For what it's worth, some of my users don't even know that 
this thing that they're using every day is called Linux under the hood. 
To them, it's just the machine that's running things like their library 
management software, or whatever.

So, as an admin, what I want from an installer is FLEXIBILITY... and not 
an "assistant" that reminds me of Microsoft Office's infamous
Clippy and
expects me to jump through burning loops to configure the system as I 
want it.

Cheers,

Niki

-- 
Microlinux - Solutions informatiques 100% Linux et logiciels libres
7, place de l'?glise - 30730 Montpezat
Web  : http://www.microlinux.fr
Mail : info at microlinux.fr
T?l. : 04 66 63 10 32