Subject: Re: VPS mailing list, BSD interest?
To: matthew green <>
From: Joe Greco <>
List: tech-kern
Date: 10/02/1996 08:55:28
> i like parts of ODS:  it keeps state in dedicated partitions on the
> disk, a metadevice db "replica".  you create several of these partitions
> on your disks and it uses them to keep state -- each one is independant
> or the others.

This works pretty well.

> i also like the model of ODS (as under solaris 2):
> 	- a metadevice acts like a normal disk partition
> 	- a metadevice can be composed of any number of real partitions
> 	  or metadevices, either concatenated or striped, or mirrored.
> you create a mirrored stripe by creating two (or three -- ODS has an,
> IMO, stpuid limit) stripes and then mirroring these two metadevices.
> recent ODS versions include raid5 support, file system extensions, etc.
> i'm fairly conversant in ODS if anyone has other questions.

ODS has (IMHO) a disadvantage...  each metadevice is only allowed to
be a partition.  CCD allows you to stick a disklabel on its "metadevice"
and you can have partition_s_.  This is maybe marginally useful, but I
happen to like it.  It allows me to build an I/O "policy" where I stripe
two drives together and simply consider the aggregate to be a faster
drive... and then I partition it up.

It requires less complexity in ccd.conf.


But..  if I could have something with all the features of ODS under *BSD..
and none of the slowdowns... I would in a minute.

... JG