Richard wrote:
> I have followed your suggestion and looked at the specs of Serial ATA > and whilst potential data transfer speed is good with a maximum of 150MB > per sec the seek times are not going to be great and certainly not in > the league of the Rocket Drive specs below. > > PERFORMANCE SPECS > Access time: 0.6μs > I/Os per second: 100,000* > Compliance: PCI 2.2 full > Capacity: 4 GB > Burst data rate: 132 MB/s > Sustained data rate: 80 to 100 MB/s > > Looking at 320 SCSI with a seek rate of around the 4ms range and a > maximum transfer rate of 320 MB per sec surely there simply is no > contest? These are I imagine internal transfer rates. However I would > be interested in knowing how important seek speed rather than data > transfer rate is when using a drive as a PhotoShop scratch disk. I am > appealing to the knowledgeable Prodigers to fill me in on this. > When ideas of Serial ATA came up about two/three years ago, it does seem like THE technology everybody's been waiting for. Faster than SCSI at a much lower price. But we don't know yet because it's still not available on the market (I might be wrong, don't really follow hardware technology anymore). On the other hand, rocket drive seems to be a harddisk utilizing RAM technology. In another word, it's a bunch of ram memory joined together to 4GB. Now everybody knows that RAM, or memory is a different kind of technology. It utilizes chips instead of magnetic discs. With this technology, no magnetic disc drives (even the fastest SCSIs or the new serial ATA) can ever compete in term of speed. This is similar to flash memory and microdrive. Microdrive utilizes magnetic discs, and it will never be able to compete in speed to flash memory. And yes, I would agree with Richard when he said: > and whilst potential data transfer speed is good with a maximum of 150MB > per sec the seek times are not going to be great and certainly not in > the league of the Rocket Drive specs below. The big numbers are normally the BUS data transfer rate. SCSI 320 at 320MB/s, SCSI-III I believe at 160MB/s, SCSI Ultra2Wide at 80MB/s, in addition to Firewire at 400 MB/s. What we need to realize is that those numbers (320MB/s SCSI, 400MB/s Firewire) are the maximum speed of the BUS. I have a 10,000rpm Ultra2wide SCSI drive and it's maximum transfer rate is only rated at ~30MB/s. Again, about two years ago when ATA100, 7200rpm drives started to come out they boast a maximum transfer rate around that of my 10,000rpm SCSI drive. (Although my SCSI has a much faster seek time). I don't know what the maximum transfer rate of today's top SCSI and ATA drives are, but I think at the most probably 40MB/s. . So unless, you're utilizing several fast drives at once, you don't really need that high bus transfer rate. In this area, the rocket drive, with "> Sustained data rate: 80 to 100 MB/s" wins again. Bus speed is like the highway speed limit. The harddisk is like your car's top speed. In america max speed you can go in highways are 70MPH. But imagine you're driving a 10hp car (whatever it is) with say a top speed of 30 MPH, it's irrelevant whether the speed limit is 70MPH or 200MPH. Similarly, firewire drives are linked via a fast bus of 400MB/s, but the physical drive itself aren't capable of filling the whole 400 MB/s bus. If you want to achieve the kind of crazy speed like that of the rocket disk, what you can do is get additional RAM (say 1-2 GB more), and get a software that will turn some portion of your ram into a virtual disk. (Reversed concept of scratch disk or pagefile or virtual memory. It's been maybe three years since I used this software, butI think you should be able to find it still. It's called Ramdisk, and the last link I have of it is http://www.jlajoie.com/ramdsk98/. Lastly, for purposes like scratch disk, I believe that you want a very fast access/seek speed--thus 15,000rpm SCSI should still be faster than 7200rpm ATA disk on this category. =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
