More SCSI questions

[Monel Funkawitz]

SCSI has my brain fried.

WTF is the difference between a IBM 18GB SCA (80pin) and a IBM 18GB (68pin) SCSI drive, besides the latter being $2 more? Which one do I want? I'm looking to go RAID 0, so do I need a RAID SCSI card, or just a regular SCSI card for hardware RAID? Whats a good RAID SCSI card if one exists?

 

[Jhereg]

<< SCSI has my brain fried.

WTF is the difference between a IBM 18GB SCA (80pin) and a IBM 18GB (68pin) SCSI drive, besides the latter being $2 more? Which one do I want? I'm looking to go RAID 0, so do I need a RAID SCSI card, or just a regular SCSI card for hardware RAID? Whats a good RAID SCSI card if one exists? >>




The difference between the two is that 80 pin incorporates power connectors into the pinout hence more pins. 80 pin is known as SCA (Single Connection Attach) which us usually reserved for high end servers with backplane connectors so one can quickly swap or hot swap drives.

Both 68 and 80 versions are found in most high end SCSI hard drives. If you have a 80 drive and you want to use it in your system you need to get an adaptor which will allow you to connect regular Molex power plug to the hard drive ( be careful if drive is LVD! make sure adaptor is apporoved for LVD!)

You need to purchase a SCSI RAID Card, availability depends on what OS you are running and how much you are willing to spend

 

[Hanpan]

80 pin scsi is hot swappable. That is the power connector is built into the 80 pins. To use this you need a computer with hot swap scsi capabilites. 68 pins is wide sicsi be it uw u2w or u160. This is essentially the same drive except it has a sererate 4 pin molex connector for power. THis drive will work with a regualr scsi adapter and teh appropriate cable. Unless you have scsi hot-swap bays you want the 68pin version. iF you do end up with an 80-pin drive adapter's are available but i and others have had some not-so pleasant experience with adapters. Also afaik 80pin drives are assinged thier id while on 68pin drives you can set them. To sum it up you want 68pin.

Again afaik win2k alows for software raid. If you want hardware raid however you will need a raid scsi card. A regular card will not be sufficient. Scsi raid cards are very expensive but adaptec does make some. I think anand uses the 2100s in one of his servers but i have heard some horror stories about this card. In fact i have heard a lot of bad things about adaptec raid cards but i don't know nor can i suggest anything better.


I hope this at least answeres some of your questions.

 

[Anon]

Just the interface difference. 80 pin has power and scsi interface in one connector, 68 pin has the scsi interface and there is a separate power connector. 80 pin hard drive are meant for hot-swap server, but you can buy a 80 -> 68 pin converter if you want. Be warned that using 80->68 pin are not recommended by the manufacturer such as the former Quantum because of possible electrical signal problem. And yet there are many different type of convectors out there (e.g. active v.s. passive termination). IMHO, if the price doesn't differ much go for 68 pin unless your RAID card has 80 pin connector. As I never own a RAID setup, I can say for sure which brand of SCSI RAID is the best, but from what I heard you can trust AMI and Mylex. Good luck on your RAID setup.

More resource:
comp.periphs.scsi FAQ
http://www.cs.ruu.nl/wais/html/na-dir/scsi-faq/part1.html

 

[Monel Funkawitz]

Thanks everyone. This is my first RAID and my first SCSI setup, so I wanna do it right.

Two 10k RPM drives at RAID 0 aught to do the trick, eh?

 

[dowxp]

u forgot $$

 

[Monel Funkawitz]

HOLY SAMBOOKA!!!

Damn, I checked out some of these SCSI RAID controllers... jeez. Most are about three feet long and are wayyyyy expensive. Looks like I'm back to one SCSI drive.

You can OC this bitch and have it crack RC5 in your spare time between writes.

 

[chuckieland]

does scsi hd offer that big performance over IDE
say 7200rpm scsi drive vs 7200rpm ide hd

 

[Monel Funkawitz]

Without bursting, ATA is up to, what, ATA100? SCSI can do 160 meg per sec, so that is over 50% right there. Add the fact that SCSI is not CPU dependant like IDE is.

 

[randomlinh]

is there any huge performance hit from using an 80pin SCA LVD drive + convertor to a scsi card that isn't LVD?

 

[bozo1]

<< is there any huge performance hit from using an 80pin SCA LVD drive + convertor to a scsi card that isn't LVD >>


Most definitely. Ultra160 is 160MBps, Ultra2 is 80MBps, Ultra-Wide is 40MBps, Fast-Wide is 20Mbps, Fast SCSI-2 is 10MBps assuming both ends are the same. You can use *most LVD drives on a non-LVD controller (assuming the drive autosenses or has a Single-Ended SCSI jumper setting) but you will only be as fast as what the controller supports.

 

[Pariah]

&quot;say 7200rpm scsi drive vs 7200rpm ide hd&quot;

SCSI will have a pretty decent advantage in access time, so under certain circumstances it will be quicker. However, 7200RPM SCSI drives are a rapidly dying breed, so most of them are quite old leveling the playing field vs current gen IDE drives, and allowing IDE to take the lead in various benchmarks.

&quot;Without bursting, ATA is up to, what, ATA100? SCSI can do 160 meg per sec, so that is over 50% right there.&quot;

Completely meaningless stat for a single drive setup. There will be zero performance difference between a SCSI 160 drive running on Ultra2 SCSI and SCSI 160.

&quot;is there any huge performance hit from using an 80pin SCA LVD drive + convertor to a scsi card that isn't LVD?&quot;

Not really. Remember, the main advantage of SCSI is the much lower access time, which is not affected by dropping the drive to non-LVD speeds. The only thing affected by the drop to non-LVD speeds is the STR which is far less important as far as performance goes for standard tasks. Not very many drives can sustain above 40MB/s (including nothing SCSI from IBM except the new 15k drive), and none can do it over the whole drive. A drop from 40MB/s on the outside of the drive to realworld SCSI UW limit of around 34-35MB/s will give you a negligible performance hit not worth mentioning.

 

[randomlinh]

oh, i know they'll be a performace hit down to whatever the max the controller can handle... i guess what I mean would there be anything more than that... cause I was talking to someone about this, and he told me that using an SCA LVD drive on a say Ultra2Wide would result in it being too slow.