Date: Wed, 4 Apr 2001 22:47:36 -0500 (CDT) From: Brennan Stehling <brennan@offwhite.net> To: Patrick Calkins <pcalkins@oemsupport.com> Cc: "'Greg Lehey'" <grog@lemis.com>, "Freebsd-Questions (E-mail)" <freebsd-questions@FreeBSD.ORG> Subject: RE: RAID Message-ID: <Pine.BSF.4.21.0104042236560.76136-100000@home.offwhite.net> In-Reply-To: <69DACACD9391054995E110C9B2819CFD0278E7@puke.oem.oemsupport.com>
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You can purchase hardware RAID systems that are managed entirely by an
internal system and FreeBSD treats the RAID as a single device. I have
worked with a couple RAID systems like this, once with Solaris and once
with FreeBSD. The first one had 4 drives in a RAID configuration and it
had a disk controller that managed the whole thing. The RAID even had
it's own CPU. I believe it was a 486 process, plenty to do the job.
And when I worked with a hardware RAID system with FreeBSD it was seamless
for me to use the RAID system. Here is the output of df on this system.
/dev/amrd0s1a 198399 37193 145335 20% /
/dev/amrd1s1e 16748555 6245519 9163152 41% /export
/dev/amrd0s1e 3473102 947042 2248212 30% /usr
/dev/amrd0s1f 2032623 949768 920246 51% /usr/local
/dev/amrd0s1g 2542344 5478 2333479 0% /var
In typical systems you have IDE or SCSI drives and you use device drivers
like ad0 for IDE and sd0 for SCSI but this one here is a MegaRAID drive in
a Dell PowerEdge server. FreeBSD has great driver support for this piece
of hardware (this brand name) and it has worked well. Dell uses this RAID
hardware in all of their systems. You could also just search out
MegaRAID. Search the mailing list archives for it and you will find lots
of information on it, perhaps my conversations on it about a year ago.
As far as configuring a software RAID with a few drives, I would not even
try it for something I want to handle high load and offer
redundancy. Yahoo I am sure uses RAID systems of a much higher level. I
was once shown a network storage system which placed on disk space on the
ethernet and if you need another 100 gigs you simply plug in a new device
and you have that space. Perhaps systems at Yahoo, Google and AltaVista
use systems such as these. The cdrom.com server runs a RAID drive for all
of it's storage. Perhaps someone knows the configuration and the brand of
hardware for that server. I heard that box is a low end Pentium with a
Gigabit ethernet connection. I would be interested in seeing a server
maintainance log on that system for the past 5 years.
Brennan Stehling - software developer and system administrator
my projects:
home.offwhite.net (free personal hosting)
www.greasydaemon.com (bsd search)
On Wed, 4 Apr 2001, Patrick Calkins wrote:
> Humm.. if the code for RAID is somewhat buggy, I was wondering what the big
> sites (like Yahoo) use to get around this... I know that Yahoo uses FreeBSD,
> and with a site as big as theirs I would think loss of data would be a top
> priority for them, hence the implementation of RAID on those boxes... any
> comments?
>
> -----Original Message-----
> From: Greg Lehey [mailto:grog@lemis.com]
> Sent: Tuesday, April 03, 2001 5:18 PM
> To: Vallo Kallaste
> Cc: Orville R. Weyrich, JR.; questions@FreeBSD.ORG
> Subject: Re: RAID
>
>
> On Tuesday, 3 April 2001 at 14:28:12 +0200, Vallo Kallaste wrote:
> > On Tue, Apr 03, 2001 at 01:16:10AM -0700, "Orville R. Weyrich, JR."
> <orville@weyrich.com> wrote:
> >
> >> I happen to have come by six identical 4.3 GB SCSI hard drives, and was
> >> wondering about an inexpensive way to make a FreeBSD server that uses
> >> them. My manual on FreeBSD covers version 3.2 -- I realize there are
> >> newer versions, but my search of the FreeBSD web site doesn't turn up my
> >> answer.
> >>
> >> Is there a way to implement RAID-5 with a couple standard SCSI
> >> controllers (the kind at eBay for under $100) or do I need to buy a
> >> specialized RAID-5 controller card?
> >>
> >> Am I asking for too much? :-) If it isn't too much, where do I go from
> >> here?
> >
> > You can use vinum volume manager, look at
> > http://www.vinumvm.org/
> >
> > Use recent -stable for implementing vinum and beware that RAID-5 is
> > considered somewhat buggy, at least that's what I gather from
> > postings in the lists.
>
> A couple of bugs have surfaced in the RAID-5 code recently. I have
> committed fixes for one, and the other is fixed but not committed.
>
> > Use two controllers, three disks each.
>
> That depends on the controllers. You could get away with one.
>
> Greg
> --
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