Which is greener?

by Administrator on June 15, 2007

The tape versus disk debate has now found a new field of battle, it seems.  At the Experis/EMC event in DC this week, EMC made the case that replacing tape with disk was the way to go (big surprise, that).  The fellow who spoke for Hopkinton enumerated the many benefits that would accrue to using tapeless VTL disk arrays to replace “older-than-the-hills” tape technology.

I had heard it all before, and I don’t buy it now.

In the Q&A phase, one smart attendee pointed out that he was trying to green his data center — mainly to reduce power requirements.  Didn’t replacing tape with disk accelerate power consumption?  It was a great question.

EMC’s response went to cost of ownership instead of green value.  I found that amusing.  The response, that you save money in labor cost savings, by substituting disk for tape, while it may have some merit, is not the answer to the question that was being asked.  Tape is still much greener by comparison.

I would be interested in someone telling me why this position is incorrect (if it is):  does a tape library with the latest high capacity media generate more heat and consume more power than racks and racks of drives providing the same capacity and always powered on?

Also, given the findings about drive failure rates in SATA arrays, do you really reduce labor expense by substituting cheap disk for tape?  I have serious doubts about this one.

{ 4 comments… read them below or add one }

Robert Clark June 15, 2007 at 1:56 pm

(I won’t get into brand names.) We have an enterprise class tape library setup for demo, and periodically the hardware gets refreshed.

When the most recent libary arrived, the power cables had smaller connectors than the previous unit. Unfortunately, the in-floor connectors didn’t match the cables.

The new model library has only two AC to DC power supplies that supply the tape drives, the robot, and all the other guts in library with power. Suprisingly, these power supplies have one C19 (15 Amp) connector on the supply side, so I was able to use two server-sized power cords to connect to standard (North America) type 110V outlets.

I don’t have a watt or amp meter handy to put in the circuit, but based on the cabling and the amount of heat the library puts off, it can’t be using more power than even one tray of disks.

And what about the energy used in producing disk drives? Smelting all the aluminum would seem to use more power than creating plastic film.

Time to start branding tape gear with a “Green Device” sticker?

jelloknee June 15, 2007 at 2:19 pm

Which is greener is irrelevant if the vendor provides a carbon neutral solution by including the offset in the price of the product (not passing it onto the customer!).

There are not many vendors that do, 3par and Object Matrix are the only ones I know of (I hereby declare a vested interest in one of the afor mentioned tree hugging storage vendors), why are the rest not following this lead?

Its true disk based systems do suck up more juice but then In my opinion its the only appropriate technology for some sectors requiring online archiving.

I might be wrong but all the extra people required to manage large tape silos all drive to work, leave the lights and PCs on in their little cubicle each evening (mainly because they are there most the night fixing issues .. sorry being silly now) and the lorries that transport the tapes from one location to another (well the tapes that actually arrive!) use lots of energy and give our children asthma … so yes go ahead and use tape , I hope you sleep well … sorry its Friday night over here and its nearly happy hour.

Disk based == plant more trees than tape.

Administrator June 15, 2007 at 2:28 pm

Thanks for the input. Actually, the issue raised by the attendee was not addressed by the EMCer. He wanted to know why he was replacing his tape based backup process with a disk based backup process when wattage is expensive and increasingly difficult to come by in the NE corridor.

TCO or appropriateness to business apps are other matters. Not unimportant ones, but different issues from the issue that the fellow was trying to address.

In my experience, replacing tape doesn’t mean that the tape mavens get laid off. Rather, they get repurposed to other work. So they are still using PCs and lamps and air conditioning at their company — the value prop of labor cost reduction doesn’t wash.

Rfc1394 June 15, 2007 at 3:17 pm

I agree in part that off-line storage is better in terms of environmental impact than constantly running disk drives. However, I think tape falls far short for the simple fact of cost per megabyte.

Last time I checked, 10″ tape reels were about $10 each, and hold about 60 mb at 6250bpi. Call it $15.00 per 100mb. That’s more expensive than a 100mb zip disk, and zip disks are terribly overpriced.

Unless they’ve gotten tremendous improvement in tape capacity, one can do DVD storage for about 20c each, which translates into 5c per gigabyte, or about $0.005 for more storage than will fit on a tape. My sister owns a consumer DVD player that stores 300 DVDs, and cost about $300, so the ability to access lots of them in near-line is already present, and quite likely for less cost than tape. If nothing else, it can allow considerably more storage space for a lot less money.

I can purchase at retail, hard drives for perhaps $80 for 200GB, which puts the price to about 4c per gigabyte, except that if you consider the reduction in cost by not expending electricity you can probably consider it a wash.

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