Date: Tue, 3 Mar 1998 20:07:05 -0500 From: Omar Thameen <omar@clifford.inch.com> To: shimon@simon-shapiro.org Cc: freebsd-hardware@FreeBSD.ORG Subject: Re: getting oriented with RAID Message-ID: <19980303200705.12976@clifford.inch.com> In-Reply-To: <XFMail.980218000230.shimon@simon-shapiro.org>; from Simon Shapiro on Wed, Feb 18, 1998 at 12:02:30AM -0800 References: <19980217150134.49019@clifford.inch.com> <XFMail.980218000230.shimon@simon-shapiro.org>
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On Wed, Feb 18, 1998 at 12:02:30AM -0800, Simon Shapiro wrote: > > On 17-Feb-98 Omar Thameen wrote: > > Hi, > > > > With DPT's single channel RAID controllers being priced at under $800 > > retail, we're looking into adding it to several of our systems. > > > > I've been reading in the archives and on Simon's website > > http://simon-shapiro.org), but there are some basic things I'm still > > not clear on that I'm hoping y'all could explain. > > > > 1) From the DPT website, their PM2044UR (single channel PCI) RAID > > controller supports RAID 0, 1, 5, 0+1, and 0+5. Does this necessarily > > mean that the FreeBSD driver written by Simon can also do all of > > the above? Something I read in the archives indicated that you > > need do use ccd for RAID0. > > Let me clarify this a bit; > > DPT always creates RAID-5 arrays by using the firmware on the HBA, and > these arrays are confined to one controller (i.e. no more than 7-45 drives, > depending on the controller and options). > > RAID-0 (striping) and RAID-1 (mirroring can be created as either firmware > controlled arrays (run dptmggr with /fw0 option), or as in-O/S driver code. > > Now, with the in-kernel RAID-{0,1} you can even create RAID-0 arrays that > are composed of other, redundant arrays. [...] I really want to make sure I understand the implementation of RAID on freebsd, because it looks like a great thing to have on production servers. Sorry if this continues to be very basic. First say I have a total of four 2G drives. I want to mirror them for redundancy, so I have 2x2G available space (I guess they would be called /dev/dpt0 and /dev/dpt1). Now say I want to optimize reads and writes, so I use ccd and make the 2x2G (mirrored) drives into one 4G drive, /dev/ccd0. If one of the mirrored drives goes bad, am I then able to power down the machine, replace the bad drive, then have the dpt manager perform its magic to recreate the data? Is ccd none the wiser? Second, I see that the "Entry Level" DPT RAID controllers run on a 68000 processor, while the "High Performance" ones use a 68040. In what types of applications does this become a factor? In the above system, I'm talking about a heavily hit pop3 or web server. Thanks once again, Omar To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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