[DRBD-user] Using RAM drives withing DRBD

Frans Grotepass frans at gatso.nl
Wed Aug 17 08:56:05 CEST 2005

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On Tuesday 16 August 2005 18:50, Lars Ellenberg wrote:
> > We have an embedded system and require an efficient and elegant method
> > of transfer from the clients to the server. The embedded clients have
> > 512MB ram and 266MHz PPC processors running ElinOS. The clients pose
> > roughly 300k-500k data per second and there are usually 4 clients per
> > system. Of the 300-500k per second, only a small percentage needs to be
> > preserved for further processing.
> >
> > Since a datastream of 300-500k to harddisk tends to trash the disks,
> > especially since it is not highly important to keep, the thought is to
> > place the data on a ramdisk. The original plan was to use rsync to copy
> > the data to the server, but since rsync can clutter the filesystem with
> > tmp files if the connection is moggy, it is not the chosen method for an
> > embedded system. I thought of using DRBD to do an intelligent sync from
> > the clients to the server. The exact architecture is not planned yet,
> > since I still need to do some tests. The data flow is exclusively from
> > the clients to the server. Other suggestions are also welcome.
Lars, thanks for the answer.

> drbd is the wrong thing to use here.

I am still setting up a test example, but it is slowly dawning on me that this 
setup might be the wrong approach. 

> consider netboot and nfs root and nfs mounted dirs.
> it may be possible to export ram (think tmpfs) as nfs.
> you then can consolidate things on the server and copy
> what you consider important to stable storage.

Well, I am looking at ssync as an alternative. The last time I used nfs was in 
'99(*) and then it was a pretty messy approach when the network or server 
went down. With an embedded system, the last thing you really want is the (I 
guess old style by now) nasty NFS disconnect behaviour.

(*)Since then I had a Linux Machine at home, but never required NFS. Just 
started again on a commercial Linux project.

> or nbd.  or iscsi.  or things like that.

Yea, so many alternatives and each has issues.

More information about the drbd-user mailing list