Date: Tue, 03 Mar 1998 16:23:24 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Wilko Bulte <wilko@yedi.iaf.nl> Cc: sbabkin@dcn.att.com, tlambert@primenet.com, jdn@acp.qiv.com, blkirk@float.eli.net, hackers@FreeBSD.ORG, grog@lemis.com Subject: Re: SCSI Bus redundancy... Message-ID: <XFMail.980303162324.shimon@simon-shapiro.org> In-Reply-To: <199803032155.WAA04054@yedi.iaf.nl>
next in thread | previous in thread | raw e-mail | index | archive | help
On 03-Mar-98 Wilko Bulte wrote:
...
> Hear hear. RAID parity is also done in hardware these days. Mostly for
> speed reasons. A second reason to go for a standalone RAIDbox is of
> course
> the clustering/multi-host thingy. Backplane RAID is IMHO more for
> low(er)-end solutions.
Where does that leave kernel RAID? I like controller level RAID because:
a. Much more flexible in packaging; I can use of-the shelf disks in
off-the-shelf cases if I choose to).
b. In the case of a DPT, you get better performance and better
reliability, as I have three busses to spread the I/O across, and three
busses to take fatal failures on.
c. I am used to it (see you argue with that :-)
...
> This is probably true. You also want to realise that the early production
> units of a given drive model tend to have substantially lower MTBFs. It
> seems when manufacturing plants get the 'feel' for producing a specific
> model MTBF gets better.
I think the focus has to change:
* We used to do RAID to protect from hardware failure disrupting service.
In the face of O/S and firmware volatility and buginess, this is absurd;
As I said, I am using DPT controllers for ALL my storage. and yet have to
loose a byte to disk failure (unless I use WD or certain Micropolis
models).
* I think RAID is only important to protect us fro mthe damage WHEN the
failure occurs.
I think the focus changed from operational feature to insurance policy.
Risk management is something not too many of us is any good at (count the
number of times you/I/we delivered a project on time.
What does it all mean? I dunno. I leave it to the scientists to ponder.
----------
Sincerely Yours,
Simon Shapiro
Shimon@Simon-Shapiro.ORG Voice: 503.799.2313
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?XFMail.980303162324.shimon>