View Full Version : Raid question

04-29-2002, 01:43 AM
while from having reviewed the information listed a ultra 160 scsi will out perform a ide raid setup, we are price constrained. Just how diference will we see comparing a Sonnet tempo RAID133 or a like device to a single pair of (small) Ceatah's? (which would max our budget)
application - DV video work.

04-29-2002, 06:22 AM
I started out with a pair of Cheetahs ( 18gig X15's) and I was getting about 120-125MB a second. With an ATA raid you will see about 70-80MB a sec So the cheetahs will be significantly faster BUT the ATA raid will be probably double what you get right now on a single ATA drive AND the ATA raid will be more than enough for DV video work

BUT if you ever plan on doing any analog video work you will definitely need the cheetahs scsi raid

04-29-2002, 12:59 PM
If you don't have the scsi controller, then you have to budget for cables and such as well and the fact you are looking at PCI IDE probably using a pre-G4 system. Which would affect what you can expect from any setup.

Anytime I hear "price constrained" and SCSI together, probably IDE. Otherwise, I'd go with one good 10k Cheetah or Atlas 10k III (they just came out with an Ultra320 revision). Two 10k Cheetahs (18G ea) would set you back $370. Controler etc extra $200-600.

Not all Macs can use an Ultra160 controller. You can use Ulta2 which supports LVD but oonly as 40 mhz mode, not 80 mhz which is what Ultra160 requires. Beige G3 may work with ATTO UL3 but not all dual function 64-bit capable boards.

Any AGP or later G4 is going to have better IDE, faster PCI thruput, and help in other ways. But you are looking at ~$400 for hard IDE Raid and two drives I suspect. And with SCSI you can add and grow. A single Cheetah 10k can now deliver 50-60MB per sec. sustained writes when used in NewWorld Mac or later.


05-01-2002, 03:13 AM
This will be for a brand new (G4) set up, as our old G3 is not up to the task of greater than 320x240. Our budget system will not easliy accomidate extensive upgrades as opposed to de novo equiptment. Also as what we have is beige G3 and we intend to use Final Cut rather than Premiere, this seems more logical.

I take it that a SCSI will be significantly faster even with a 2 drive array. It will allow the option of making it a 3 or 4 or... drive array over time, while IDE RAID will be locked in as 2 disks. Our only trade off is loss of capacity... favoring a second IDE or firewire externals as a mass storage site. I take that there is a thought favoring SCSI over IDE despite the higher cost (ie it IS worth it.)

Is there anything to the "matched drives" in arrays? ie will there be problems adding an extra drive to the array sometime later? or in working with some of our external ultra160 9 Gb drives via the same controler?

05-01-2002, 10:48 AM
I take it that a SCSI will be significantly faster even with a 2 drive array. It will allow the option of making it a 3 or 4 or... drive array over time, while IDE RAID will be locked in as 2 disks.

No, IDE Hardware RAID cards support either 2 or 4 drives installed. Increasing the number of drives from 2 to 4 does not make them faster but it does make them larger.

SCSI is faster, but do you need more than 60 to 80 MB/sec through-put? That should determine which you use. Don't let price set your purpose. You need what you need.

The nice part about scsi is scalability. You can start out with a good card (UL3D or UL4D) and smaller less speedy and less expensive drives. As you grow you can add larger/faster/newer drives. When you add a new pair or more of drives to a SCSI bus you would be able to RAID them together and leave the older drives in place in their own RAID array. Having multiple arrays is possible with software RAID configurations.


05-01-2002, 05:51 PM
One comment - perhaps off topic a bit - but the hardware RAID cards assume that you are installing internally. I'm using an external hardware RAID box that using an IDE -> LVD SCSI backplane to set up 6 x 100 GB IDE drives as one virtual ~ 500 GB RAID 5 drive. It's connected to my Miles2 card in my 7300, the miles 2 is already driving 2 internal 18 GB LVD drives and 4 external 36 LVD SCSI drives in a Burly - and it all works - quite well in fact, with Granite cabling. BTW all but the IDE array are from the 'Gurus...

so...you can make HUGE IDE drive arrays (in fact up to 12 drives in one case design) but that's running an external array, and it would involve purchasing a SCSI card (although there are Firewire versions out now) and paying for the external case / power supplies and the like.. But still - for $5300 CDN, to get > 1/2 terabyte of storage in a 19" rackmountable enclosure...


05-02-2002, 07:01 PM
Hey Rick

I thought I read somewhere that if you install 4 ATA drives on a raid card you end up with 2 volumes ... one from the master drives and one from the slave drives Can you confirm this? (or can you tell me I have been drinking my supper again?)


05-02-2002, 09:59 PM

In trying this it looks like there is no way to separate the drives from a physical standpoint. Install 4 drives on a Acard hardware RAID card and turn on the RAID you will have one big volume using all four drives. You would have to partition it to break it up, as far as your computer is concerned you have one big drive.

The reason you get no performance gain by adding 2 more drives is that IDE only accesses one drive at a time on a channel. 2 channels will access 2 drives. Even the fact you doubled the buffer doesn't matter, the channel only accesses one drive at a time. (in SCSI RAID0 when you increase drives and total buffer size you will realize big gains in throughput as the buffers and drives are added together and accessed concurrently)

Kaye tried 2 Acard Hardware RAIDs with 4 IBM 120GXP drives and then SoftRAIDed the 2 hard-RAID arrays together. He didn't get much at all in improvement over the single array, seems to be the rule with ATA software RAID, never a significant performance gain.