Date: Wed, 11 Aug 1999 05:41:24 -0500 (CDT) From: Joe Greco <jgreco@ns.sol.net> To: mike@sentex.net (Mike Tancsa) Cc: freebsd-scsi@freebsd.org Subject: Re: External RAID boxes (was Re: AHC errors. Bad disk or bad Message-ID: <199908111041.FAA94114@aurora.sol.net> In-Reply-To: <3.0.5.32.19990809164854.01c08750_staff.sentex.ca@ns.sol.net> from Mike Tancsa at "Aug 9, 1999 8:51:10 pm"
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> >Based on what I found in raid.pdf, I think it might be worth asking > >Legacy if they use raid controllers made by Mylex in their arrays. > > > >A lot of RAID kit is oem'd and that model number sounds very familiar :) > > > >> Management Port > >> Cause: The SmartARRAY cannot establish > >> communication with the DAC960 hardware > > Wow! As my hockey coach used to yell, "Good eye!". Thanks for pointing > that out. > > What I am not clear on from glancing at the mylex site is that they seem to > be cards only and cards with boxes ? Am I right in thinking that you > supply the case ? From the .pdf file > > "The DAC960S is designed to fit anywhere inside a disk array enclosure, > including in a 5-1/4" inch drive bay. And you don't need disk driver > software, because it interfaces directly through a SCSI adapter. An > optional DBX960S distribution board fits together with the DAC960SU edge > connectors, and provides standard connection for both the host and drive > channels and the serial and I/O ports. Or, the DAC960SU can be plugged > directly into the array's backplane. " Here's the deal. Mylex makes the DAC960 series controllers. There are a number of options, including differential, UW, etc. AFAICT, their primary market is the OEM market, which integrates Mylex controller cards into custom arrays. Lots of companies like MTI are doing this. The OEM versions often have various different firmware changes, etc. Mylex also makes the DAC960 in a "standalone module", i.e. something you can integrate into a disk subsystem yourself, or that smaller OEM's can integrate without getting quite down to the board level. This is a 5.25" FH deep form factor "can" which has a bunch of connectors on the back and an LCD panel on the front. The back will have your SCSI connectors and power, serial ports, and other signalling (if you use/need it). The DAC card inside slides in from the front into a card edge connector in the back, very straightforward design, you can open the front and take out the DAC controller itself (upgr, replace, etc) without disassembling your server. You can get either product, canned or just board-level. If you get board- level, I believe that you can get parts of the can (like the PC board in the back that has the card edge connector to accept the actual DAC card, which has the SCSI/power/serial/etc on the other side of it) separately. That's your "distribution board", and you'll need one. Now, I've been buying these suckers, but only two variants... The DACSXIH-2W-16M-MYL is a canned ultra-wide controller that has 2 drive chains and a host chain, and 16MB RAM. I order these all with minimal RAM since I pull the factory RAM and recycle some of the 64MB parity SIMM's we have laying around - the unit requires two SIMM's and you can go up to two 128's, but for my uses, 128MB total is great. The Mylex RAM is relatively expensive, IIRC. This board essentially has 3 SCSI controllers, and is the same as the next controller except it lacks an additional 3 controller daughtercard. The distribution board (either alone or part of the can) will have all six connectors regardless. The DACSXIH-5W-16M-MYL is the above controller with an additional 3 controller daughtercard. However, this adds an option: you may use it either as a 1-host 5-drive SCSI bus setup or a 2-host 4-drive SCSI bus setup (meaning you connect two hosts to two separate ports, allowing the hosts to share the Mylex). The daughtercard plugs in to the DAC card, and also has a card edge connector to plug in to the distribution board. In both of these hardware configurations, you may "double up" and buy an additional SXI to act as a redundant controller, you can hook them together and they'll also work together to increase performance. Most of the OEM's (MTI, etc) do this. I don't use this myself so I won't comment beyond saying that my one-Mylex-RAID-array was performing as well as a dual-Mylex-OEM-RAID-array I had access to for a while. Probably limited mostly by disk I/O more than anything else. There are other variants too. Visit the Mylex web site for details. Now, the advantages I see in getting the SXI over the SX board level product: 1) It's self-contained. You supply power and SCSI interconnects, and maybe a serial port for console. 2) It can be configured (not tweaked, but configured) from the front LCD panel or the serial port. 3) It looks cool. The disadvantage I've seen: It's a 5.25" FH _deep_ form factor, meaning that it is longer than your typical bigass 5.25" FH drive. I can barely put one of these into an Enlight midtower ATX or an Antec rackmount ATX case along with an ASUS P2B-DS motherboard (it can be done but your choices are limited and the result is a bit annoying). A more general disadvantage to the whole DAC960 is that the number of things that you can get to from the LCD/serial port is a bit disappointing. You can do all basic admin operations (create/initialize/change state/check consistency/etc) but some of the more obscure tunables aren't available in this manner. My own solution was to cobble together a DOS boot disk that has Mylex RAIDFX for DOS on it, along with the Adaptec ASPI driver for the P2B-DS, which I use for configuring the controller initially. This sucks since I recently inflicted some "damage" to my array that required the use of the utility to fix it, and had it been a thousand miles away I would have been a bit ticked off. In defense of the Mylex, I did something rather bizarre that I knew I shouldn't have, and besides, the controller _can_ be talked to via the SCSI bus (RAIDFX does), so it'd just be nice to see a FreeBSD RAIDFX utility (I'll keep wishing and praying). This doesn't reflect poorly on Mylex, though, IMHO. I've seen horribly unusable LCD displays on lots of equipment: the Mylex LCD/serial is _very_ useful, functional, and easy to use. I just can't tune some things I'd like to. > Do you save substantially 'putting it together' yourself ? Dunno. I don't think you'll save anything in terms of frustration spent trying to get it to work, if you're missing something that you need. > What sort of price have people paid (in USD), and who is generally a good > outlet to buy from ? Been getting the DACSXIH-2W-16M for ~$2050 from Tech Data or Ingram (Ingram? I think...?) The -5W goes for $500-$800 more. Tech Data doesn't seem to carry them in stock, Ingram does but Ingram charges a bit more. The last two -5W's I got from TD arrived about two weeks after ordering, but some previous -2W's that were ordered went on backorder for over a month before we cancelled the order and bought from Ingram. If I recall correctly, the suggested markup on these is _fantastic_. :-/ > Thanks for any input anyone can provide on this topic. They're good units and I'm very happy with mine. As with any RAID5 controller, the performance isn't necessarily everything you could hope for, but it is several times better than the DPT PC card controllers I tried out, and as far as I can tell the limiting factor with the DAC is the drive array - not the controller. ... Joe ------------------------------------------------------------------------------- Joe Greco - Systems Administrator jgreco@ns.sol.net Solaria Public Access UNIX - Milwaukee, WI 414/342-4847 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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