classiccmp server hardware

From: Rob O'Donnell <>
Date: Mon Oct 11 13:43:27 2004

At 16:12 11/10/2004, Fred N. van Kempen wrote:

>On Mon, 11 Oct 2004, Jochen Kunz wrote:
> > It depends on the load that the server already has and how much overhead
> > software RAID1 causes. Typically RAID1 doesn't cost that much CPU. To
> > the past - present comparision: CPUs got a _lot_ more faster then disk
> > dirves in the past 20 years. See the thoughts behind the BSD LFS.
>I have never trusted OS-level disk redundancy schemes, and never
>will. Promise controllers have strange ways of doing things, and
>most certainly do require OS-level software assistance. Disks
>attached to a Promise RAID1 controller can be taken off the Promise,
>and attached to a regular IDE port, and will work as-is. Typical
>RAID controllers that do hardware-supported RAID store state and
>config info on the attached drives, so they usually claim a few
>sectors for that.

In my experience, running servers purely as a hobby, I've found the version
of RAID1 as presented by cheap ATA controllers on FreeBSD more than
adequate, a considerable speed up than a single drive, and definitely
better than not having a raid, when a drive goes down!!

I've used various cards (mostly SiL 0680 chipset) on FreeBSD without
problem. At least on the 0680, they do write something to the disc, as
taking the drives out of one machine and putting them on a different card
in a different machine caused them to be spotted as a RAID pair before the
OS had even had a chance to boot. Drives can be removed, and they do work
on their own however too, so I don't know what gets stored where?

You can mirror on FreeBSD using either vimum, which is pure software raid
and will work across any drives no matter what types or controllers they
are on (even a mix) or for most ATA IDE RAID cards, the ata driver has
built in support (`man atacontrol`) which I presume negotiates with the
card bios and sorts out who does what.

Oh, as far as the SiL0680 specifically is concerned, from personal
experience FreeBSD 4.10 works fine... 5.2 works, but 5.2.1 panics on boot
(even booting the install). Later snapshots are OK again though, but for
the moment 4.10 is still recommended for production servers, at least until
5.3 is out, which is apparently only a couple of weeks off. 5.3 apparently
offers some new facilities (geom_vinum and gmirror) but I've not used them,
or anything later than 5.2 yet, just seen them discussed while sorting out
beta bugs on the freebsd-current list.

Received on Mon Oct 11 2004 - 13:43:27 BST

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