CacheFS: front filesystem vs. cached filesystem (what's the difference?)

CacheFS: front filesystem vs. cached filesystem (what's the difference?)

Post by Richard D. Davis, Jr » Tue, 26 Mar 2002 05:28:06



I've been reading about CacheFS, and it's clear to me
that the "back filesystem" resides on the remote host,
and it contains the data being cached locally.  

But I'm confused about the terms "front filesystem" and
"cached filesystem".  It's obvious that both are local
filesystems, but...

Do the terms "front filesystem" and a "cached filesystem"
refer to the same thing?

-or-

Is a cached filesystem made up of possibly several front
filesystems?

What's the difference?

Thanks,
Richard Davis

(Woodridge, IL)

  rddavis1.vcf
< 1K Download
 
 
 

CacheFS: front filesystem vs. cached filesystem (what's the difference?)

Post by Edwar » Tue, 26 Mar 2002 10:53:11


I'm trying to fathom cachefs myself

Back file system: obviously the remote one
Front file system: the local file system where the cache will live
Cache file system: local mount point of the resource to be cached. e.g. back
fs is server:/usr/local mounted to cache fs /usr/local
Cache directory: location of cached data e.g. /var/cache stores all cached
data for cache fs /usr/local.

There can be only one cache dir, so the contents of the cache dir on the
front fs will be the cached data for all cache file sytems in use. Each
cache fs is identified by a cache ID (used to delete cache fs's)

I haven't fully grasped the difference between a file system and a directory
(I'm ashamed to say) so I'm struggling to visualise the front fs AND the
cache directory



> I've been reading about CacheFS, and it's clear to me
> that the "back filesystem" resides on the remote host,
> and it contains the data being cached locally.

> But I'm confused about the terms "front filesystem" and
> "cached filesystem".  It's obvious that both are local
> filesystems, but...

> Do the terms "front filesystem" and a "cached filesystem"
> refer to the same thing?

> -or-

> Is a cached filesystem made up of possibly several front
> filesystems?

> What's the difference?

> Thanks,
> Richard Davis

> (Woodridge, IL)


 
 
 

CacheFS: front filesystem vs. cached filesystem (what's the difference?)

Post by Philip Bro » Tue, 26 Mar 2002 15:49:55



>...
>There can be only one cache dir, so the contents of the cache dir on the
>front fs will be the cached data for all cache file sytems in use.

says who?
You can specify different cachefs filesystems for each mountpoint,
OR share them. Your choice.
As far as I know, you can use cfsadmin to create separate caches on
separate local disks.
You can certainly create multiple, since I just did so.

mini overview of cfsadmin usage:
   cfsadmin -c /cachedir1
Then you can mount something using cachefs and specifying use of /cachedir1.
There will then be a directory-looking thing created under
/cachedir1 which will be the cache store for that mount.
It will have a name similar to the "back filesystem", but you dont normally
have to worry about the exact name.

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CacheFS: front filesystem vs. cached filesystem (what's the difference?)

Post by Marvi » Tue, 26 Mar 2002 19:32:02



> I've been reading about CacheFS, and it's clear to me
> that the "back filesystem" resides on the remote host,
> and it contains the data being cached locally.  

> But I'm confused about the terms "front filesystem" and
> "cached filesystem".  It's obvious that both are local
> filesystems, but...

> Do the terms "front filesystem" and a "cached filesystem"
> refer to the same thing?

> -or-

> Is a cached filesystem made up of possibly several front
> filesystems?

> What's the difference?

> Thanks,
> Richard Davis

> (Woodridge, IL)begin:vcard
> n:Davis, Jr.;Richard D.
> x-mozilla-html:FALSE
> adr:;;;;;;
> version:2.1

> x-mozilla-cpt:;0
> fn:Richard D. Davis, Jr.
> end:vcard

CacheFS is actually a File system which uses LOCAL file system for a
cache from other file system (usually NFS). It cames within Solaris 2.4.
AFAIK, it is not memory cache like the "cache" is known for.
 
 
 

1. How to cache the /usr filesystem with CacheFS?

Solaris 2.4 kernel patch 101945-13, according to its README, is
supposed to fix this bug:

    1177600 No way to cache the root and /usr file systems with CacheFS

So far, I've been unable to locate any documentation on how to setup a
dataless client so that its /usr filesystem is cached with CacheFS,
e.g., what exactly to put in /etc/vfstab etc.

I once tried this before 101945-13 had been released and (obviously)
had all sorts of problems.  This time, I'd like to know in advance
what I'm supposed to do.

I'd appreciate any configuration hints on this issue.

Thanks in advance,
Michael
--

WWW:   http://www.inf.tu-dresden.de/~mh1/

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