Drive Speed Comparisons - 7200RPM vs. 5400RPM in RAID?

O asks: "Looking at Pricewatch for new drives, it seems that the prices for a 60GB 5400rpm drive and a 40GB 7200rpm drive are about the same. I do have ATA/100 RAID on my motherboard, and I'm wondering how a striped RAID of 5400rpm drives would stack up against a single 7200rpm drive? I could sure get a hell of a lot more storage for the money. Any Slashdot readers have experience with this?"

Comments

RAID VS Single Drive -- RAID, but not for performa

[depeche]

The performance will depend on the application mix you are using. How much data can the drive continiously stream in/out which is the dependant on the drive and the bandwidth of the controller. Are you needs read intensive, write intensive, random or linear in nature? I would almost always recommend using hardware raid to anyone because you get reliability, which is probably more imporant anyway. A stripped RAID array will be able to provide better read throughput, especially as the number of drives goes up and the reads can be spread accross multiple heads. If you are doing random editing of high bandwidth video, however, you probobly want mirrored high RPM drives. This allows for full spead reads and writes, and redundancy. If you are doing lots of writes, especially in small chunks, stripped RAID is not going to be as fast--too much parity calculation. Also, it depends on the quality of the hardware RAID implementation, the saturation of the bus (are you going to run your ATA/100 drives as masters in independant channels?) etc.

You will probobly be better off getting something which meets your needs rather that worrying about the best performance. So my suggestion would be RAID for the added safety value (not to mention that unless you need it, more space will probobly be worth more than a few milliseconds of performance gain). Remember though, RAID doesn't save you from powerfailures! If you are going to have any stripped RAID array, even hardware, you must have it on a UPS so that it is not left in an inconsistant state! Good hunting!

Go 7200RPM

[acidblood]

In terms of throughput, yes, you'll get about the same performance. However, unless you spend all day loading large files from a completely defragmented partition, what you should really look for is reduced seek times. This is the bottleneck when doing 99% of the work in your computer -- and that's why solid state drives are so blazingly fast, despite having an inferior throughput than their mechanical counterparts: they have smaller seek times, by many orders of magnitude.

Smaller seek times can be achieved by various means:
1. Get a high-end drive. More expensive models feature faster actuators.
2. Reduce the physical area the disk can access, by partitioning accordingly. Seagate also used this trick with their first-gen X15 drive, by reducing the platter size from 3" to 2.5", and they were very successful.
3. Use RAID 1 (mirroring) with a good controller, which for IDE basically means the 3ware models. They are, far and away, the best. Besides shaving off the seek times, they also improve the throughput.
4. And, of course, the most important: get a hard drive which spins faster. If you don't believe me, take a look at the sites below for benchmarks.

The hard drive is the only peripheral nowadays whose access time is measured in miliseconds and not nanoseconds. Instead of buying loads of memory and the fastest processor available, everyone should pay attention to the storage side of their machines -- whoever has experienced 10k and 15k RPM disks finds it hard to go back.

The best places in the web for storage info are Storage Review and, to a lesser extent, x-bit labs. Storage Review, besides their extremely scientific methodologies, maintains a drive reliability database, so you can check whether the drive you're looking for is likely to fail.