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  • SCSI vs. IDE

    Greetingz
    Can anyone tell me whether the greater cost of buying an Adaptec 2940U2W to use with a Quantum Vking II and a Plextor 40Max is worth it?I know that the hardware is of better technology and that SCSI HDD are the best but is the performance compared to that of a Ultra66 HDD really better for a good desktop system.

    (This doesn't have anything to do with Matrox boards.It's a general question since I'm gonna buy a new computer in the near{I hope} future}
    Thanx and C YA

    ------------------
    -=Jimmy=-
    -=Jimmy=-

  • #2
    Thanks for taking the time to help me LastOne.Although I don't want to question your knowledge on the SCSI bus are U totally sure that using a U2W HDD with an UW controller like AHA-2940UW will still give me 100% of the performance of the HDD.It souns correct to me as well for the maximum com speed of the viking surely isn't more than 15 MB/s and the one of the 40xmax much less but R U sure?I mean there ain't much point in buying SCSI if it ain't gonna perform well.Thanx again.

    PS. I don't plan on using a lot of devices.
    Maybe 2HDDs a CDROM and CDRW and a scanner which gives a total of 5 so combined com speed shouldn't be an issue.


    ------------------
    -=Jimmy=-
    -=Jimmy=-

    Comment


    • #3
      Yes, it's true that a U2W drive on a UW controller won't have it's performance affected, my IBM 9LP drive is U2W and my controller is only UW. The only effect will be that the burst transfer rate of the disk will be 40MB/s rather than 80MB/s but that's only a consideration if you're just going to be reading the same sector on the disk over and over and over...

      Couple of considerations about mixing UW and U2W devices though:
      You may need to change the drive from LVD mode to SE (single ended) mode so it can talk to the UW bus.

      U2W drives don't have any termination so you have to add an active terminator or make sure the drive is in the middle of the chain and the Plextor is terminated, ie. the cable will look like this:
      Card------Viking------Plextor

      If you get an U2W controller then you can't mix UW and U2W drives on the same cable, there will be seperate connectors on the card for UW and U2W.

      Comment


      • #4
        Come on guys! think logically about this: what application on a desktop computer will ask for a transfer rate of ( UW) 80 MB/s ? These harddrives were designed for servers and raid systems: the drives are fast, but it's the pathway TO and FROM the drive wich are capable of large amounts of data transfer(when ten users are requesting information stored on the drive simultaniously that's what these drives were designed for) I do agree that SCSI is preferable when it comes to stability and compatibility, I do use a scsi cd-writer and cd-rom drive. But did you know that most of the drives ultra /ultrawide only differ in connection to the drive? (costs only 500 U.S. dollars more (actually 1000,- dutch guilders)). So my advise concerning scsi: always ok, but if you need more mb's same performance (or little less, hardly noticible) take IDE.

        Comment


        • #5
          Pretty much any application which is loading data will be able to process it faster than a physical medium like a hard disk can supply it. The number of users accessing a drive is irrelevant, any multitasking situation will see several programs accessing different parts of the disk simultaneously. What isn't irrelevant is the fact that most SCSI drives can supply data at higher rates and with lower latency than their IDE siblings. SCSI drives are expensive, but they are high performance, high reliability devices and are suitable for any high performance situation, not just servers.

          Most SCSI drives are in no way related to the IDE drives from the same manufacturer, SCSI drives tend to have much lower data densities and they will have completely different electronics. Also, Ultra2Wide SCSI drives tend to be cheaper than the Ultra and UltraWide configurations of the same drive...

          It would be pointless to say that SCSI drives are ideal for every situation, in most cases an IDE hard drive with SCSI CD/CDR setup is more applicable. If you require (or just want ) absolute speed and reliability then SCSI is a no-brainer. For good comparitive benchmarks of SCSI and IDE drives take a look at www.storagereview.com .

          Comment


          • #6
            I'm not exactly sure myself and that's why I asked LostOne.But based on the research I've done for myself I think he's right.It ain't then fact that the U2W SCSI bus has a burst speed of 80MB/S cause I don't think that the average speed of the best SCSI HDD exceeds 20MB/S(although burst speed can well exceed this limit},not even the fact that the SCSI bus,contrary to the IDE bus is multichanneld. What really makes the difference is that SCSI HDD are far better than HDD ones.
            Although this ain't by far necessary it still ain't absurd if you wan't a quality system.

            BTW LostOne.Why are Ultra and UltraWide drives more expensive than the better U2W versions.I bet it's because these HDD's(like for example the cheetah series}are really aimed at servers and workstations right?


            ------------------
            -=Jimmy=-
            -=Jimmy=-

            Comment


            • #7
              To the Q. regarding the U2W-HD drives being cheaper than the counter parts UW & U, I think the answer is found by looking at the number of U2W-drives being sold. It is larger than for the other two types. This increased production volume makes the electronics cheaper thus making the drive cheaper.

              By the way, I totally agree with LostOne. Listen to the wise words and learn.

              Just my two cents.

              Ghydda

              Go a head - see if you can find any IDE units in my signature!

              ------------------
              A slowly desintegrating nobody with an Athlon 500 MHz on a FIC SD11 with 256MB Memorycard, Adaptec 2940UW, Adaptec 2904CD, 3 SCSI HD, JVC cooking equipment, Plextor 40Max, Pioneer DVD-U03S, SBlive Value with homemade S/PDIF I/O-card and last but not least - Matrox Marvel G200 AGP 16MB SD with PowerStrip@110/147

              Only thing missing: Matrox RT2000
              As I always say: You can get more with a kind word and a 2-by-4 than you can with just a kind word.
              My beloved Parhelia was twotiming with Dan Wood - now she's gone forever and all I got is this lousy T-shirt
              |Stolen Rig|RetroGames Rig|Workstation Rig|Server Rig|

              Comment


              • #8
                Assuming you already have the Viking and the Plextor then you only really need an UltraWide card like the 2940UW, the U2W will do nothing for you since neither of these devices will even push the 40MB/s of the UW spec.

                SCSI hard drives do make a difference on a normal desktop PC, but are much more expensive. SCSI CD/CDR drives aren't that much more expensive than their IDE counterparts and are generally far superior in quality, features and speed.

                To summarise the IDE/SCSI debate:
                SCSI:
                Varies from fast to very, very fast
                Supports command queing so multitasking and use of multiple devices is efficient
                Mixing older and newer SCSI devices on the same channel does not impact performance (eg. a SCSI-2 and Ultra device on the same channel still means the Ultra device can transfer 20MB/s)
                Supports large number of devices per channel (up to 15 on a wide interface)
                Supports a large variety of internal and external devices (hard drives, CD, DAT, tape, scanners, printers etc etc...)
                Generally expensive
                Generally high quality

                IDE:
                Slower than SCSI, but still fast
                Only 1 device can use the bus at a time and until the device frees the bus no more commands can take place
                Mixing slow and fast IDE devices will slow down the fast device
                Only 2 devices per channel and IDE cable lengths make external connections rare
                Generally cheap
                Generally built down to a price which affects quality (the number of IDE CD drives that have died on me after a year or two...)


                For my own computer I chose to go all SCSI, I have an IBM 9ES 4.5GB HD, IBM 9LP 9.1GB HD, Plextor 32x UltraPlex, Plasmon 4x8 CDR and external Syquest SyJet 1.5GB drive. It's a dual Celeron 550 and it's very, very fast and very, very reliable (under Linux that is ).

                Comment


                • #9
                  I just put together my second all-SCSI system. The first one has been working well for 2 1/2 years now. The technical key, I think, to SCSI's higher performance is the controller. It takes a huge load off the CPU by taking over much of the I/O duties. Using IDE (even DMA) still puts greater load on your CPU on average.

                  All the other benefits Lost One has mentioned, except one. If you know you will be using SCSI, get it built onto the motherboard. The motherboards that have SCSI are generally top-notch in their own right, and built-in SCSI is less expensive and cleaner inside your case.

                  Pay attention, however, to the features of the controller. There are differences. I got a Tyan Thunderbolt motherboard in large part because of the Adaptec AIC-7896 controller on board. It's the only slot 1 board out there with this controller. (also an awesome board in just about every way imaginable.) The 7896 is a dual channel U2W controller. There is a point in this, which is, if you are going to use an LVD U2W hard drive, even on an U2W controller, its performance goes down to UW specs if there are any non-U2W devices on the same channel. True, any normal desktop will rarely, if ever, have need of the full bandwidth U2W provides, but if you do add more drives later it can make a difference. I have a Seagate Cheetah on channel A and a Plextor Ultraplex Wide CDRom on channel B. The dual channels also give you more flexibility in assigning addresses, since you double your capacity to 30 devices. Add all the hard drives, removable media drives, scanners, CD-Roms, DVD, CDRW, etc. you want to, and keep 'em all SCSI.

                  ------------------
                  Kind Regards,

                  KvH




                  [This message has been edited by KvHagedorn (edited 09-20-1999).]

                  Comment


                  • #10
                    Thanx to everybody out there for taking the time to post (really long) messages.I know SCSI's not exactly worth every buck you pay since UDMA66 7200RPM IDE drives R getting pretty fast but it still is worth it for now.
                    BTW is the ADAPTEC AHA-2940U2W a dual channel SCSI controller?

                    ------------------
                    -=Jimmy=-
                    -=Jimmy=-

                    Comment


                    • #11
                      Yes, the Adaptec 2940U2W has 2 channels, one ultra2 LVD channel with internal and external 68 pin connectors and one "regular" ultra channel with 68 pin and 50 pin connectors on it, both internal. You can buy an internal to external adaptor if you need to hook up external devices to the regular channel, but it tends to get complicated if you have internal devices on that channel as well.

                      Comment


                      • #12
                        Ah SCSI versus IDE...
                        Here's my story

                        I once had a SCSI HD named quantum fireball FS (or something familiar). I was a newbie in the scsi HD issue, and made a mistake.

                        I am very sensitive to noise (I'm not a wacko or something, I just hate that brrrrrr at 2 am in the morning while I read posts at this forum ). Anyway, I took out the CPU fan, replaced it with a "not so fast but silent" fan, which was placed at my videocard. I also added another "not so fast but completely silent" fan at the back, extracting hot air.

                        Then, I pitched down the PSU fan.

                        This rendered my case 20 degree celcius hotter. With that setup, I added a SCSI hd to my new asus P2l97 with scsi on-board.

                        After a few days the HD made a very very very LOUD beeeeep, and while the beeeep lasted, the computer froze, thus starting again when the beeeep was finito.

                        After another few days a few clusters at the HD got marked "bad".

                        I of course opened the case every now and then to really confirm the frightening beeep came from the new quantum scsi HD, and while doing that, I also noticed that it was hot like hell itself. Damn I almost burned my fingers at it!

                        I eventually excanged the SCSI HD (yup, that dumb sales-man gave me a new one). In my present situation I have the same old quantum fireball, and a new, judged as to be quiet and "chill", IBM UltraStar 4.5 U2W LVD, being cooled down by another "silent and slow, but oh so effective" fan in the front.

                        So, what I'm trying to say, do a little research, find out what SCSI HD's run cool and, if you like, quiet. By that one and by golly, make sure you give it high-quality cooling

                        Gosh did you really read all that? cool man... ¦ )

                        ---------------------
                        One thing about my Aunt Nadie: She was gruff on the outside, but if you ever needed something, like a spanking or a scolding, she'd give it to you.

                        Comment


                        • #13
                          Wow, tish. Looks like you learned the heat lesson the hard way (as most of us do). I replaced the hd in my old mac once upon a time with a quantum and the noise was like 10 times worse than before. That's probably how I live with my half height 10,000 rpm IBM ZX now. This thing is LOUD and runs HOT. Funny, since I stuck it in a heatsink on top of my case and aimed two 60mm fans at it, it seems to run quite cool.

                          BTW, my Seagate Cheetah doesn't get nearly as hot or scream nearly as loudly, but the Tim Taylor school of fan overkill is still lots of fun. (right, Paul?)

                          ------------------
                          Kind Regards,

                          KvH


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