Please explain SCSI to me

wizardmaxx

wizardmaxx

wizardmaxx

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Ok so far I've determined that a 80pin HDD can be used on a 68pin controller card with either a backplane or adapter.

Next thing is the U160 vs U320 issue. Will a U320 80pin hdd run on a U160 controller card or does it have to be U160 with U160 and U320 with U320.

:confused: :confused: :confused:
 
wizardmaxx said:
Ok so far I've determined that a 80pin HDD can be used on a 68pin controller card with either a backplane or adapter.

Next thing is the U160 vs U320 issue. Will a U320 80pin hdd run on a U160 controller card or does it have to be U160 with U160 and U320 with U320.

:confused: :confused: :confused:
Click to expand...

You can quite happily run a U320 disk on a U160 controller and vice versa.
 
So the difference is really the bandwidth and thats it ?

Also what benefit would it be to get a U160 controller that can take extra memory(ie 128mb upgrade)

Thanks RPStewart. Now help me take better photos. Bought my first DSLR two weeks ago :p
 
wizardmaxx said:
So the difference is really the bandwidth and thats it ?
Click to expand...

Pretty much, the bandwidth is shared between the devices on the cable so the more bandwidth is available a) the more disks you can have before you saturate the bus and obviously b) the faster you get the data.

Also what benefit would it be to get a U160 controller that can take extra memory(ie 128mb upgrade)
Click to expand...

Memory backed cards are really only of benefit if you're looking for redundancy, the memory holds data which hasn't been written to the disks in the event of a power failure. Personally I'd go with a U320 card if you can but unless you can use PCIe or PCI-X there's no point because it'll be limited by normal PCI.

Thanks RPStewart. Now help me take better photos. Bought my first DSLR two weeks ago :p
Click to expand...

Take lots, the law of averages says at least some must be good - it works for me ;)
 
No. That card is PCI-X (64bit, 66MHz PCI slot). The slot you're referring to is PCIe, totally different stuff.

The adaptec card will probably work in a normal PCI slot if you have one spare but it'll kick down to 32bit 33MHz signalling with the consequent 133Mb/s bandwidth limit so it'd be a bit of a waste really.

There's a Dell server card which appears on eBay quite a lot that has been mentioned on here before but it's an 8x PCIe card so you'd need a 16x slot for it. I forget off the top of my head who actually makes it.
 
The 39320 will work in a 32-bit PCI slot, but as stated bandwith will be limited. However the blisstering fast Randam Access time <3ms (Atlas II) which they can acieve due to the 15k spindle speed is hardly effected if at all by the 32-bit/33mhz bus.
 
Interesting, I have always been interested in scsi, are these hard drives faster than raptors even though you have to use a pci card? Are there any downsides to using the drives, are they noisy?
 
A decent SCSI setup is scarily fast but scarily expensive, £500 for 130Gb isn't uncommon.

Modern 15Krpm SCSI drives are a lot faster than raptors - Seagate quote 125Mb/s sustained transfers from a Cheetah 15K, a Raptor will give 80-90Mb/s. That sort of speed is fine over PCI for a single drive but two or more will saturate 32bit PCI which is why the vast majority of SCSI controllers are 64bt PCI-X now.

The drives themselves are far from quiet, the main market for these things is in servers so acoustics are secondary to reliability and performance.
 
the.m said:
...are these hard drives faster than raptors...
Click to expand...
SCSI's been faster for years...
There are now 20k drives. :D
(2 x the spindle speed of raptors)

A card is the same as using an on-mobo controller and/or SATA Controller card.
IE - Just the same.
Remember peeps putting in a IDE Controller card so they could run ATA100 HDD's on their mobo's with ATA33 controllers?
So the card itself doesn't slow anything down...

But, if you have an array that can transfer data at 200mb/s, and your interface (PCI) can only do 133mb/s... THAT would slow it down.

But with PCI-E slots/cards - No slowdown. :)
SCSI > SATA in terms of speed (even when SATA first came in) and is far more mature... But also a lot more expensive.
(I run a Raptor as it is the right £/speed for me - Have SCSI kit, but for tape drives and the like)

EDIT - I type slow. :(
And yep - The drives are not terribly quiet.
In fact - It's quite a comforting whine, if you like whines.
 
Check out Tekram SCSI cards as well as Adaptec. From personal experience I have found that Adaptec bump the price up due to their name. Tekram still uses decent LSI chipsets, but also tend to bundle in the cables and terminators. (These bits can add £30 or £40 to the bill.... my first 8-headed SCSI cable cost me £80 in 1996)

The TekRAM card in my sig is a U320 PCI-X card, but also runs happily in my PCI bus at U160 speeds.

SCSI is darn expensive... but blisteringly fast. Very noticable when installing games, programs, encoding video, etc. Much faster than my mates SATA RAID setup...

Do a search in this forum and you will find loads of threads like this one. Lots of info in there. (I know I have posted the links to the SCSI FAQs many times....)

Go for multiple disk setups to get even more from the speed. (Especially get that swap drive out onto it's own fast SCSI drive for example...)


As to noise.... well... I have a house of buzzing PCs. And only realised quite how noisey it all was when I had a power cut and was hit by a wall of silence..... :D
 
So looking around there are lots of scsi cards about, some of them show a maximum data transfer rate, some are 20mbps others are 40mbps, are they good or bad, should you go for more?
 
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