How fast will the SCSI go..?

troe666 used Ask the Experts™
I have an Athlon XP based Windows XP machine that currently runs an ATA 100 5,400rpm 20gb drive as it's main drive.

I have in my hot little hands a HP Ultra 10K SCSI-3 drive with the hot swap plugs and also another HP 10K SCSI2 LVD drive.

My question is this - I can only use a SCSI card I have here, an Adaptec 2940UW card with the 68pin etc connections - but what will performance be like?

Or, more specifically, will performance be better than the current ATA100 drive in there..?

They are both 9.1GB drive models but are server-type drives not installed as yet, they are new. I have read on the product specs that the 2940UW supports SCSI1,2,3,and UW so it should support both the SCSI2 LVD/UW and also the SCSI3 right..?

Please let me know as I am dying to know if I should even both with copying the partitions etc and going through the general associated pain if performance will not be much better? both SCSIs are 10k rpm drives whereas the IDE is only 5,400rpm and if the 2940UW supports the SCSI1,2,&3 then there should be excellent performance? or am i missing something?....If necessary, I can run only the SCSI3 Ultra 10k drive on the scsi card, hence one drive can make full use of its bandwidth, even if its not the newest card..?

what will it go like?? or with both new scsi's connected, for instance? please help
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The problem here is the LVD.  You must use a SCSI card that is LVD.  You cannot mix "standard" SCSI and LVD.

I sugggest an Adaptec 29160N as a current model SCSI adapter that supports LVD.


OK I got that part then, but is it then possible to use the 2940UW to control the SCSI3 UW drive? I am just about to get the adapter to plug it into the port on the controller, as at present it has the hotswap port.

Will it provide good performance still? I know I could go buy the latest adaptec card, but I want to know how the Ultra 3 10K will go in SCSI3 mode on the 2940UW...apparently it supports it (on


You CAN use the 2940UW with the SCSI3 UW drive.  You may need a special cable or adapter to get the connectors to mate.

The performance will be good but not as fast as the drive is capable of.  But certainly not what I would consider POOR performance.
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I've got (amongst other devices) an Atlas III and an Atlas V controlled by a 2940UW myself. Altas V has a U-SCSI 160 interface (68 pin). The 2940UW does so too, so no special cables are required.
Performance is 12-15 MB/sec.
Even if you could get the SCSI devices working, you're not going to get better than SCSI-3 performance.  You're looking at 20MB/sec (burst speed, not sustained) at best.  If you're interested in speed, stick with your ATA 100 (100 MB/sec burst speed).

The real perks to SCSI (and the reason its used in high end servers), is off-loading processing to the SCSI bus and better performance when using more devices.  If you were running RAID 0 or 5 (data striping), you would get a bit of a performance boost, but I still doubt you'd reach the speeds of the ATA100 drive (assuming you have an ATA100 controller).  RPM is great, but if the bus isn't fast enough to read the data, it doesn't matter how fast it spins.

To put this in perspective, you're talking about SCSI technology that's about 3 years old (if not more).  Back then, it was substantially faster than the IDE drives of the day.  But compared to more recent ATA interfaces, you're better off with the ATA.
Dave PuseyIT Support Specialist

No comment has been added lately, so it's time to clean up this question.

I will leave the following recommendation in the Cleanup topic area:

Accept comment from mntgomery

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Dave Pusey
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