Peter Tribble wrote:
On 4/24/07, Darren J Moffat <[EMAIL PROTECTED]> wrote:
With reference to Lori's blog posting[1] I'd like to throw out a few of
my thoughts on spliting up the namespace.
Just a plea with my sysadmin hat on - please don't go overboard
and make new filesystems just because we can. Each extra
filesystem generates more work for the administrator, if only
for the effort to parse df output (which is more than cluttered enough
already).
My first reaction to that, is yes, of course, extra file systems are extra
work. Don't require them, and don't even make them the default unless
they buy you a lot. But then I thought, no, let's challenge that a bit.
Why do administrators do 'df' commands? It's to find out how much space
is used or available in a single file system. That made sense when file
systems each had their own dedicated slice, but now it doesn't make that
much sense anymore. Unless you've assigned a quota to a zfs file system,
"space available" is meaningful more at the pool level. And if you DID
assign a quota to the file system, then you really did want that part of
the name space to be a separate, and separately manageable, file system.
With zfs, file systems are in many ways more like directories than what
we used to call file systems. They draw from pooled storage. They
have low overhead and are easy to create and destroy. File systems
are sort of like super-functional directories, with quality-of-service
control and cloning and snapshots. Many of the things that sysadmins
used to have to do with file systems just aren't necessary or even
meaningful anymore. And so maybe the additional work of managing
more file systems is actually a lot smaller than you might initially think.
In other words, think about ALL of the implications of using zfs,
not just some.
We've come up with a lot of good reasons for having multiple
file systems. So we know that there are benefits. We also know
that there are costs. But if we can figure out a way to keep the
costs low, the benefits might outweigh them.
In other words, let people have a system with just one filesystem.
I think I can agree with this, but I'm not absolutely certain. On the
one hand, sure, more freedom is better. But I'm concerned that
our long-term install and upgrade strategies might be constrained
by having to support configurations that haven't been set up with
the granularity needed for some kinds of valuable storage management
features.
This conversation is great! I'm getting lots of good information
and I *really* want to figure out what's best, even if it challenges
some of my cherished notions.
Lori
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