[Linux-cachefs] Re: CacheFS

[Erik Mol]

Hello Andy,

Great work on the Gentoo CacheFS wiki.
http://gentoo-wiki.com/HOWTO_CacheFS

Still some of the CacheFS parts are still a bit vague to me.
FScache!=CacheFS!=Cachefiles(d)

As I understand it now:

FS-Cache is a part of the Linux Kernel which intermediates between  
'network based filesystems' (AFS/NFS) and a cache back-end.
FS-Cache is designed to work with a cache back-end of choice.

Cache back-ends:
CacheFS can act as a cache back-end to FS-Cache and runs on top of a  
block device thus providing its own filesystem.
CacheFiles can act as a cache back-end to FS-Cache and runs in  
directory on top of another filesystem.

We are using and talking about CacheFiles(d), right?

Since I do not have the knowledge to modify a RHEL4 distribution to  
get it to work with FS-Cache I decided to try out RHEL 5 Beta 2.
Which should have support for  FS-cache (mentioned as CacheFS in  
featurelist as on http://www.linuxcompatible.org/ 
Red_Hat_Enterprise_Linux_5_Beta_2_s76179.html).

Since I would like to use local caching with NFS for increased  
performance I tried compiling Cachefilesd on my RHEL5B2 testsystem.
File compiled just fined using just a make, I moved the necessary  
files, utilized init.d. file, created seperate cache disk.
I then set extented attributes on the cachedisk, checked the  
cachefiles config, ran cachefilesd and mounted my NFS volume.
Things looked fine in the messagelog. The cache and graveyard  
directory were created.
After copying a file from the NFS volume things got written to my  
cache folder just before cachefilesd stops.

Any hints on what I am doing wrong?

Messagelog:

Dec  6 11:57:58 RHEL5B2 kernel: EXT3-fs: mounted filesystem with  
ordered data mode.
Dec  6 11:58:07 RHEL5B2 cachefilesd[2116]: About to bind cache
Dec  6 11:58:07 RHEL5B2 kernel: FS-Cache: Cache "mycache" added (type  
cachefiles)
Dec  6 11:58:07 RHEL5B2 kernel: CacheFiles: File cache on 08:11  
registered
Dec  6 11:58:07 RHEL5B2 cachefilesd[2116]: Bound cache
Dec  6 11:58:07 RHEL5B2 cachefilesd[2117]: Daemon Started
Dec  6 11:58:07 RHEL5B2 cachefilesd[2117]: Scan complete
Dec  6 11:58:37 RHEL5B2 cachefilesd[2117]: Refilling cull table
Dec  6 11:58:37 RHEL5B2 cachefilesd[2117]: Scan complete
Dec  6 11:58:47 RHEL5B2 kernel: FS-Cache: netfs 'nfs' registered for  
caching
Dec  6 11:59:07 RHEL5B2 cachefilesd[2117]: Refilling cull table
Dec  6 11:59:07 RHEL5B2 cachefilesd[2117]: Scan complete
Dec  6 11:59:37 RHEL5B2 cachefilesd[2117]: Refilling cull table
Dec  6 11:59:37 RHEL5B2 cachefilesd[2117]: Failed to check object's  
in-use state: errno 95 (Operation not supported)
Dec  6 11:59:37 RHEL5B2 kernel: CacheFiles: File cache on 08:11  
unregistering
Dec  6 11:59:37 RHEL5B2 kernel: FS-Cache: Withdrawing cache "mycache"

I will CC this to the mailinglist, we might get someone else to respond.

Regards,

Erik