On 4/26/07, Lori Alt <[EMAIL PROTECTED]> wrote:
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.
True, but it's actually quite hard to get at the moment. It's easy if
you have a single pool - it doesn't matter which line you look at.
But once you have 2 or more pools (and that's the way it would
work, I expect - a boot pool and 1 or more data pools) there's
an awful lot of output you may have to read. This isn't helped
by zpool and zfs giving different answers., with the one from zfs
being the one I want. The point is that every filesystem adds
additional output the administrator has to mentally filter. (For
one thing, you have to map a directory name to a containing
pool.)
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.
Oh, I agree. The trouble is that sysadmins still have to work using
their traditional tools, including their brains, which are tooled up
for cases with a much lower filesystem count. What I don't see as
part of this are new tools (or enhancements to existing tools) that
make this easier to handle.
For example, backup tools are currently filesystem based.
Eventually, the tools will catch up. But my experience so far
is that while zfs is fantastic from the point of view of pooling,
once I've got large numbers of filesystems and snapshots
and clones thereof, and the odd zvol, it can be a devil of
a job to work out what's going on.
--
-Peter Tribble
http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/
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