Re: to lvm or not to lvm?
Greg Folkert wrote:
On Tue, 2007-05-01 at 10:39 +0800, Bob wrote:
Andrew Sackville-West wrote:
8< snip lots of automatically growing partitions using LVM stuff
I'm trying to think of a way an admin coming for the Windows world, or
from a home server world, where they've had the convenience of not
having to think about these things and you've either got harddrive space
or you don't, can have a that convenience while retaining the extra
security of having lots of partitions with different functions that
can't steal space from each other. I don't know how common it is for a
live fs resize to go south, if it's a statistically significant
percentage then obviously it wouldn't be worth the risk, if not I still
think it's a good idea.
Why are you after this complexity of automatically growing partitions?
disk space is cheap. recovering from problematic fs resizes is NOT. I
understand the idea of tuning your partition sizes so that you can
have the optimal size and this is very doable with LVM, but if you've
got portions of your directory tree that might grow really big, then
just give them the space and be done with it. It you later determine
that you don't need it all, you can adjust then with LVM with relative
Think about this then. LPARs on an IBM machine. LPAR allows you to
"redistribute" processors and memory to logical machines. The hypervisor
gives you the ability to "add processing power" to a logical machine or
"add memory" or to remove them.
This give you flexibility to control your "domains" and flow the
resources depending on your needs. Then think about doing LVM with those
guys. Sure does throw a monkey wrench in thinking about that.
<fx_Otto> Wow man that's trippy </fx Otto>
As far as resizing, AIX has been doing it for years, both resizing
larger and resizing smaller. Though the "growing" is much more tested,
the shrinking does works well.
As long as it's reliable
I agree simplicity=good complexity=bad, but sometimes it's worth adding
two measures of complexity to an automated system in order to remove one
from user, or in this case admin, space, particularly if you can do it
in a relatively easy to understand way, such as with well documented
shell scripts, getting called by a disk space monitoring daemon.
that said, you may of course do whatever you like to your system. And
the idea sounds cool on the face of it. I just think you're asking for
trouble and unneeded complexity.
Auto adding of space has been done. Trust me on this one. Don't do it.
I've seen the after effects. A typo in a script can do more harm in 20
seconds (or less) than any one person could do in 20 years when dealing
with disk space. You would be well advised to setup an existing projects
disk space monitoring system and have it urgently mail you that disk
space is becoming a premium commodity on /blah filesystem.
As long as it's not possible for a growing partition to take space away
from another partition, I can't see how this would do anything but give
you more time to react, you run your messed up script that starts
pushing the contents of /dev/zero into a text file and eating harddrive
space, if your sitting next to the machine you see the HDD lights come
on and hear the seeking, if your remote the first clue you get is an
email or SMS saying /blah has been automatically grown by 5GB because it
was more than 85% full,  you can kill your script, delete the text
file, reduce the partition again and nothing crashed, if all it had done
was email you a message pointing out /blah was running out of space, and
/blah was also required by some other vital process that ran out of
space and crashed before you could kill the script, you'd wish you had
I think the best way to implement it would be to set limits on how much
a partition can grow, so once /blah has eaten 90% of the remaining
space, it's not allowed to grow any more and the processes responsible
for the expansion, along with any others that require space on /blah,
crash hopefully not taking the whole system with it but still leaving a
good chunk of space for other vital partitions to grow into, should they
need to, so when you get off your train, plain or hobby horse, hopefully
you can still ssh in and fix things.
Anyway, I've got so many projects on at the moment I probably won't have
time to do anything about it, it's fun to kick the ideas round though.
Even a better to use someone else's work. ZENOSS http://www.zenoss.com/
Works wonders. It has beaten HP's OpenView and IBM's Tivoli regularly
outperforming them and delivering better flexibility and presentation of
Interesting, I'm thumbing through the documentation now.
 actually when I've made a asinine mistake like that  I usually
realise it just as I hit enter, ever installed lilo on /dev/hda1 when
that was your uncles Windows 2000 partition, I have, it feels stupid 
 notice i said *like* that, which means not *actually* that, though I
don't delude my self that I'm never tired, hungover or daft enough to do
that accidentally, I haven't yet.
 I got all the data off and did a reinstall but it was hard, shameful
Garrr, do your bit for global warming, become a pirate, you can "borrow" my copy of Windows 95 if you want.