[rrd-developers] Alternative to rrdcached on linux - rrdfs - FUSE based RRD caching
peter at stamfest.at
Wed Feb 24 09:42:15 CET 2010
Tobias Oetiker <tobi at oetiker.ch> schrieb am 23.02.2010 23:28:53:
> Hi Peter,
> wow ... sounds impressive. Have you done performance evaluations ?
Only insofar, as it is fast. Accessing RRDs in /dev/shm is just "wow". I
wanted to do my first real deployment of the software yesterday, and then
I stumbled across rrdcached. And my motivation just vanished :-(
> If you could apply your genius to rrdcached and maybe make it even
> better based on the insights gained from the rrdfs implementation?
Well, I had some plans for rrdfs:
- Provide a memory only version of rrd_update_r. Then I could get rid of
the staging area and just cache RRDs entirely in memory - while still
providing file-level access to them.
- The write ahead logging rrdfs is able to do would allow for proper
restart of a crashed/killed/whatever rrdfs in such a scenario (but it
would also help for the staging-area case).
- Make it NFS capable: Access RRDs handled by rrdfs from a remote host
using normal file access. This requires a recent kernel and has some
drawbacks, though. But this would allow for HUGE RRD repositories -
distributed over any number of NFS servers.
- It would even be possible to integrate more of rrdtool commands into
rrdfs. Just imagine a mechanism to just access a png file by name and have
it automagically computed from memory. It would even be possible to
provide "pseudo" directories for every RRD, eg. containing RRD data as CSV
"files". The sky is the limit (or the avoidance of feature creep)...
I don't know the inner workings of rrdcached, but rrdfs could actually
become part of it, I think (#ifdef'd on the availability of FUSE). The
question is: Is this something you would accept?
So a plan could be:
- factor out file access from rrd_update_r and provide a rrd_update_mem_r
as a base for rrd_update_r and become memory only (with the transparent
permanent storage handling).
- integrate the IPC handling from rrdcached into rrdfs or vice-versa.
This MIGHT be as simple as just modifying the main() from rrdfs to fire up
a single pthread and have that take care of rrdfs and all the rest would
be handled by the existing rrdcached (plus the backend storage/update
caching would have to be integrated - in that area I'm using a hashtable
keyed on the file name essentially containing a dynamic array of updates
> Today Peter Stamfest wrote:
[.. removed ..]
Dipl.-Ing. Peter Stamfest UNIX, Networking & Computing Consultant
Tel: +43/699/10711205 Software Development - Internetservices
E-Mail: peter at stamfest.at WWW: http://stamfest.at/
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