Where are the High-Capacity SCSI Drives?

An anonymous reader asks: "Storage technology has really exploded in recent years, giving us ATA drives up to and exceeding 200-250 GB per drive. Why is it that SCSI drive technology has remained stagnant? I can't find a SCSI drive exceeding about a 146 GB capacity. Instead, businesses (and some individuals) wanting greater storage capacities are required to buy more drives which takes up more space, generates more heat, provides more points of failure, uses more electricity, etc. Why is this so?"

Comments

My Guess

[MBCook]

My guess is a simple one. Who buys SCSI stuff? It's expensive so it's mostly businesses and others who need high reliability (which one of the major reasons SCSI is more expensive). Now while normal people can "afford" to lose 250, 300, or more GB of data, for a business that could be worth billions of dollars.

The solution to this reliability problem is the RAID. There are two RAID levels that are ideal (there are more, but this is a simple explanation). There is 1, which is just a mirror; and 5, which is striping with parity.

With RAID 1, if you have 500 GB of data, you would need 2 500 GB drives. You lose 50% of the capacity you buy. The other option is RAID 5, where you lose (1/number of disks). So you could store 500 GB of data on 6 100 GB disks. This way you've only lost 100 GB of storage to redundancy as opposed to 500 GB.

So when businesses want to store large ammounts of data, it's more economical to use many smaller drivers than to large drives. Even if you don't need the redundancy (for example the disk is just being used for temporary storage while working on large digital picture or video files) they it's still better to use many small disks. While using a 500 GB drive will only go so fast (lets just say 60 MB/s sustained), by using a RAID, you can mulitply that. So by using 5 100 GB drives, you might be able to sustain 300 MB/s (assuming the bus can keep up, etc). Even if you only scale at 50% (that would be 150 MB/s) that's still 2 to 3 times faster than a single drive. That performance can save you money.

So, if you can afford it you can get much better performance or economics from using multiple smaller drives from one large one.

That's my theory/understanding. Begin tearing it apart!

Re:My Guess

[innosent]

Gamers? How many gamers really NEED large (>147GB) disks? SCSI drives are not produced for gamers, they are produced for business workstations and servers. I agree with you about SCSI being better, but the reasons you gave don't apply to all IDE controllers (number 1), and certainly not to all SATA controllers/disks (all reasons). A GOOD (i.e. usually not onboard, probably something from 3ware, etc.) SATA controller has a processor, command-queueing, separate, bi-directional channels for each device, and SATA connectors are designed for hot swapping (better than SCA actually, even to the point of connections being made in sequence due to staggered pins). I've got a 12-disk SATA RAID-5 array at work, and don't have any of the problems you listed, because I hand-picked the hardware to avoid those (and other) limitations. If you really want your games to run as fast as possible, then it's going to cost a few thousand dollars anyways, and if you really need that much space, maybe it'd be a good idea to buy a decent controller.

Re:They do exist!

[Pegasus]

Heck, give me then 3600rpm disks with transfer speeds of 20mb/s and capacity of 2Tb! I'd gladly have dozen of them to put my dvd collection on.

I've heard some things about the new Hitachi 400gb drive being optimized for tv settop boxes. Does that mean that it's optimized for linear reads/writes? If so, why did they not decrease rpm in order to gain more capacity?