[OpenAFS] What filesystem?

Steve Simmons scs@umich.edu
Wed, 8 Mar 2006 13:21:15 -0500

On Mar 7, 2006, at 4:55 PM, Christopher D. Clausen wrote:

> Jeffrey Hutzelman <jhutz@cmu.edu> wrote:
>> Back in the 1980's (long before I got to CMU), a few people had a
>> grand vision.  They imagined a world in which every student and staff
>> member had his or her own small computer.  All of these machines
>> would be similar hardware and run the same software, maintained and
>> distributed by a central support group, which would also manage the
>> machines so that individual users wouldn't have to know how.
> I think this is where UIUC differs.  The problem is that there  
> isn't a single entity managing all computers (as is the case at  
> most schools.) There is a centrally maintained Active Directory  
> domain, with seperate OUs delegated to various other autonomous  
> groups: http://www.ad.uiuc.edu/

It sounds like UIUC is similar to University of Michigan, where the  
administration strongly encourages decentralization. At one time UofM  
had more than a half-dozen AFS cells in it, each run by different  
departments with different rule sets.

For fiddily stupid reasons, the main campus AFS service (called IFS,  
as I slip into UMisms below) charged too much for IFS space and  
didn't supply much in terms of large quotas. This changed a year or  
two back, and the result is that departments are finding they can get  
AFS space from the IFS service cheaper than they can run it  
themselves. Of the existing campus cells I know of, all but two are  
scheduled to or in the process of converting to using central IFS.  
One of those is the research cell at CITI, which will probably never  
go away, and one is at a school which has some severe restrictions on  
what they can do with their data due to medical and research privacy  

Since the changes to storage charges and quotas, IFS space has been  
growing spectacularly. Our usage is up 50% in the last 75 days. The  
advantages of a campus-wide filestore (especially when backed by what  
is effectively a campus-wide single sign-on; see <http:// 
www.umich.edu/~umweb/software/cosign/>) are huge.

AFS/IFS has historically not supported Windows nor MacOS well. This  
seems to be changing, but other folks can speak to that better than  
I. If/when it does, I expect IFS to start making more inroads in  
those communities on campus.

But there will always be a need for local file store, where 'local'  
is a deliberately vague word. We have departments or groups which  
need multiple terabytes of disk for a weekend of heavy-duty data  
crunching. No network-attached file server is going to serve that  
data across gigabit links and give adequate performance; SANs might  
but who can afford to borrow a SAN for a weekend? Only departmental- 
level storage is going to meet those requirements.

I guess my point is that AFS is *an* answer to file system issues,  
but there is not and likely will never be an answer to *all* file  
system issues, regardless of centralized vs decentralize or  
commercial vs. academic. Bleeding edge research using large bulk data  
needs its store 'close to' the CPUs, as does corporate data mining.  
Regulatory issues sometimes mean that file store cannot be  
centralized without putting the entire central support staff (and  
file store) under onerous requirements. Sometime Micro$oft trumps  
everything. There's a mix, there's always going to be a mix.