1TB Raid?

[CogoSWSDS]

The local Circuit City has a 1TB Western Digital MyBook mirrored external USB drive for $289. I assume by "mirrored" it's probably some sort of RAID other than RAID 0. Any ideas what RAID level this drive is? Is $289 a good deal for a 1TB USB 2.0 RAID? A regular 1TB MyBook costs $232 at the local Best Buy.

I'm thinking about getting one or the other of these drives for backing up my Digital8 tapes for when my camcorder eventually wears out. Which one do you think - the mirrored or unmirrored drive? 1TB will hold about 76 hrs of DV-AVI.

Thanks,

CogoSWSDS

[rallynavvie]

I assume by "mirrored" it's probably some sort of RAID other than RAID 0.

Simple mirroring is RAID 1. For a backup drive that's exactly what you want. If one drive fails or gets a bad sector it will switch to the other drive which may not have the error. Depending on the controller the other drive can then be rebuilt from the one good drive in order to get everything back to 100%.

This is a good reference to the varieties of RAID if you want to do some reading:
http://www.pcguide.com/ref/hdd/perf/raid/levels/

[mpack]

I would be very wary of buying a large capacity drive (RAID or not) with a USB2 interface. First off, you will no doubt need an external power supply, so you can forget easy mobility. Then you will quite likely find that throughput is intolerably slow - so slow that the drive might end up being a paperweight in a relatively short time.

I would have thought that an e-SATA RAID enclosure was a better bet.

[edDV]

A USB 2.0 drive runs about half the speed of an internal drive (~20-30MB/s). It is however more than fast enough to play DV files with reliability (DV runs ~3.8MB/s at 1x speed).

[RabidDog]

I would def get an e-sata .. 1tb would be hell to fill up on USb2.0. I have a 160g usb2.0 drive and I find myself waiting, any time I use it.. it doesn't seem like much but it gets real old , real soon. A gbEthernet might also be a workable solution. mirrored normally means two drives holding exactly the same info, so maybe 500gb storage only?. Also mirrored drives are slower than a single drive on writing.

[mpack]

A USB 2.0 drive runs about half the speed of an internal drive (~20-30MB/s).

USB is a packet based protocol with lots of overheads, so I think that getting 30MB/s would be pretty good going for a USB 2.0 device. I suspect that a carelessly implemented device might give you a lot less than that, and certainly the external USB 2.0 HDDs I already own feel like they get a lot less than that (though it's hard to be sure whether to put blame on the device or the OS). I would certainly be worried about making a bad buy because of these concerns.

IMHO, USB just isn't designed for high sustained throughput. Firewire is better for this application, eSATA is currently best.

[edDV]

I agree but I have measured my USB2 drives at a max of 30MB (240Mb/s) sustained on a couple of Core2 Duo machines. Core2 Duo laptops seem to run slower. These drives are limited by the USB2 interface, eSATA drives are limited by the drive's hardware performance.

[rallynavvie]

You're all forgetting that USB 2.0 is exceedingly more common than either eSATA or FireWire. For simple compatibility USB is still king. The best option is to have an enclosure that supports all three.

For a backup drive I think it's irrelevant anyway. I tend to do my backups while I'm sleeping. Using the backup image from the USB device is still quicker than spanned DVDs. Even for file backup it's really only cloning content that is present on your internal HDDs anyway so faster access to it may not really be an issue.

[mpack]

You're all forgetting that USB 2.0 is exceedingly more common than either eSATA or FireWire. For simple compatibility USB is still king.

No, I'm not forgetting how convenient and compatible USB is, how could I when I use it every day?

But, USB has its limitations, and in this application the superior compatibility of USB is not really an advantage. This drive will not really be a portable drive (I'm assuming it will be bulky and need mains power), so in practice it only needs to be compatible with one host PC. In this scenario I would go with eSATA even if it means having to buy an additional SATA controller card for that PC (as in my case it would, since I'm already using both native SATA channels for internal HDDs).