Esoteric Hard Drive question?

Discussion in 'Mac Pro' started by snagitseven, Jan 24, 2008.

  1. snagitseven macrumors member

    Jan 12, 2008
    I'm moving from a 7 yr old G4 Sawtooth 1.4GHZ OS 10.4.8 with 3 internal 36/72GB Seagate SCSI drives hosted on an Atto UL3D ultra scsi PCI card (3 yrs old) to a new Mac Pro 2.8GHZ dual quad running 3 SATA II internal Seagate 7200.11 500GB/1TB drives. Can anyone offer an idea, "apples to apples", if I should expect slower, faster or about the same overall real world hard drive performance? I realize the MP will scream in comparison for memory related operation, video, etc. but I'm trying to understand the HD only "bottleneck" difference I'm likely to experience. No raid on the G4 or planned for the MP at this point so not looking for Raid comparsions - yet.
    I know generically ultra Scsi 320 is faster than SATA II but I'm guessing new technology, controllers, etc. should make my MP be at least as fast, hard drive-wise, as the old G4 w/Scsi.
    Any thoughts?
  2. Random Chaos macrumors member

    Jan 16, 2008
    Well, HDD read speeds are generally much slower than the busses they run on. To use the bus to potential, you need an optical or other non-magnetic disk based drive. So, the limiting factor will be the internal read/write speeds, seek speed, spinup speed, and cache size/speed. That info requires you to look up the specific drives in question. Without knowing the models and brands, there is little we can say besides: You probably won't notice much difference unless you are doing heavily HDD intensive applications :)

    This is why people use RAID striping - it allows faster read speeds of the media. But even that there is a lot of debate over whether it gives any measurable real world benefit for the home user. Sure it is faster, but does the home user really need that minor boost of speed for a significantly costlier setup?

    As an example, take for instance the Samsung 500GB HD501LJ drive. It is specced to transfer 135MB/s from the disk to the buffer and 300MB/s from the buffer to the host. The limiting factor is the 135MB/s from disk to buffer. That number seems quite high from what I remember from 3rd party speed tests, so that's probably peak transfer rate, not average. But either way, you can see the limiting factor isn't the bus.
  3. contoursvt macrumors 6502a

    Jul 22, 2005
    6 months ago at my work, we built some cheap PC's, (5 of them) with E6300 core2 duo CPUs, 2GB RAM, 73GB 10K Raptor sata drive for the boot and 250GB for the data drive and low end 7100GS video cards.

    After finding the system pathetic compared to my home computers which all have SCSI stuff, I pulled the Raptor and tossed in an ancient 2940U2W controller in a PCI slot and an ancient Quantum Atlas 10KIII drive.

    In benchmarks like throughput, sequential reads..etc. The Raptor murders the old SCSI setup, but you'd never know that when you use the computer. The old 10K SCSI setup while getting half the benchmark scores, feels at least 30% more responsive overall. Much more pleasure to use.

    So many people will disagree with me I'm sure but I think in real world usage, your ancient SCSI drives and controller (if put into a new Mac Pro) would feel and perform better for day to day tasks than a current 7200RPM SATA drive. Access time is more important 99% of the time than transfer rates. Thats just my opinion.

  4. snagitseven thread starter macrumors member

    Jan 12, 2008
    Thanks for sharing your experience with a Mac to PC example.
    I am not planning to try and move the ATTO card and scsi drives to the Mac Pro (or a PC) so the comparison doesn't quite answer my query. I was trying to get a feel of comparison of the old set up vs the new set up or in other words, old G4 w/scsi vs MP w/Sata II, hard drive-wise.
    I know I'll find out soon enough but wanted to reset my expectations beforehand so I wouldn't be disappointed.
  5. TyleRomeo macrumors 6502a

    Mar 22, 2002
    New York
    It's not the interface it's your drive speeds. Your SCSI drives can't touch 50MBps each. The platters on them are so small. Both Seagate and Samsungs latests drives do over 100MBps each. Even getting two SATA drives raiding them will destroy your old 3 drive SCSI system.
  6. contoursvt macrumors 6502a

    Jul 22, 2005
    Linear read speeds dont mean much unless you plan on doing a copy of a single large unfragmented file to a destination which also has a huge amount of open space with no fragmentation with an equally fast write speed.

    Its very important to pay attention to access times as well as how well the interface behaves under heavy loads. ATA133 (IDE) interface had fast theoretical speeds and sucked when dealing with multiple requests coming from all over.
  7. benpatient macrumors 68000

    Nov 4, 2003
    Short answer to your question.

    If your boot (system) drive is set up in a RAID 0 array, then it will be noticeably faster in every way than the old SCSI system.

    If not, then big transfers will happen faster, but random access things will be the same or slightly slower, because the drives you are used to are faster and more efficient at getting to things randomly.

    People dog RAID 0, but it's fast. As long as you're making backups of important things, you'll be fine.
  8. snagitseven thread starter macrumors member

    Jan 12, 2008
    BENPATIENT, thanks much for the very helpful info; now you've got me seriously rethinking Raid 0 (which I've never done..). Couple of questions/thoughts before I order the drives:
    1. HD 1 and 2 - Can I set up 2 1TB drives for HD1 and 2 w/2 partitions each, one for system stuff, one for storage files (500gb or some other matched size on each)? Is there a performance hit if raid volumes are partitioned like this?
    2. HD3 - (500gb as ordered from Apple in Mac Pro build) would be for bootable system safety clone back up
    3. HD 4 - 1TB partitioned for CS3 PS/Bridge scratch disk (250gb) and Time Machine (750gb). 250gb for CS3 scratch too small?
    4. Can a pair Raid 0 configured volumes be backed up to a single drive, ie. external or internal (to my HD #3 as above for system volume?)
    Does this setup make any sense for Raid 0? Or would you recommend a different configuration.
    Thanks for your advice (or anyone else who wants to wade in on this).

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