Date: Tue, 26 Aug 1997 22:28:42 -0700 From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@MindBender.serv.net> To: Tom <tom@uniserve.com> Cc: FreeBSD <freebsd@synertec.ene.unb.br>, stable@freebsd.org Subject: Re: DPT scsi card Message-ID: <199708270529.WAA25841@MindBender.serv.net> In-Reply-To: Your message of Tue, 26 Aug 97 21:16:49 -0700. <Pine.BSF.3.96.970826211447.12208D-100000@shell.uniserve.com>
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>On Tue, 26 Aug 1997, Michael L. VanLoon -- HeadCandy.com wrote:
>> You can do RAID in software with the ccd (concatenated disk) driver.
>> There are FreeBSD and NetBSD servers running this all over the place.
>> It's rock solid extremely fast.
> I wouldn't call ccd a RAID solution. The "R" in RAID stands for
>redundant, and ccd has poor support for that.
While that was the original "definition", RAID had become to be known
for more than simple redudancy in common usage. Striping without
fault tolerance is a very common usage, which generally falls under
the term "RAID-5", if I'm not mistaken.
>From what I understand, ccd can be used for mirroring. However,
recovery in case of failure is not automatic, and you can't mix
mirroring with striping.
So, yes, if you're using ccd to stripe for performance, you don't get
any redundancy features with ccd. If you use it for mirroring, it's
likely that you won't get any performance benefits.
DPT controllers are reported to do all that stuff transparently in
hardware. And, the FreeBSD driver supports basic functionality on DPT
cards. However, it isn't clear how much advanced functionality the
FreeBSD DPT driver supports.
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Michael L. VanLoon michaelv@MindBender.serv.net
Contract software development for Windows NT, Windows 95 and Unix.
Windows NT and Unix server development in C++ and C.
--< Free your mind and your machine -- NetBSD free un*x >--
NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
NetBSD ports in progress: PICA, others...
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