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Zero Striped Array RAIDs twice as fast?

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February 5, 2009 8:22:52 PM

I seem to remember years ago reading a piece where Tom did a comparison between the speed of a Zero Striped Array (say, 2x80GB) versus a single drive (say, 160GB) and that the speed increase of the RAID was 99% faster -- almost twice as fast.

Is this true?

Otherwise, what is the general speed increase of a Zero Striped Array versus a single drive?

Any feedback is appreciated.

defender

February 5, 2009 11:23:56 PM

Theoretically it should be double however, it will depend on the drives used, the controller used the OS used... basically everything. I would expect to see anywhere from a 50% improvement to ~95%ish as youll never get a 100% improvement.
a b G Storage
February 6, 2009 9:31:04 PM

Well, it won't double due to the identical seek time. It will improve though.
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a b G Storage
February 6, 2009 9:59:04 PM

Keep in mind that the only thing that will increase is the drives read and write speeds. This does not mean that your games load time will be cut in half. This is because there is a lot of CPU time needed to load a game, not so much reading.

Without knowing what your computer is, and what you want it to do, its impossible to say whether AID0 is a good idea for you. I do know that most of the time, its not.
a b G Storage
February 7, 2009 10:39:01 AM

RAID'd drives are able to maintain higher sustained throughput. If you are moving large files around all the time, yes the speed of the transfer can be nearly double.
For everyday use though, what makes more of an impact is access speed.
The average person will get more benefit from a drive that can read many smaller bits of information fast (a single drive with low access times) than a RAID'd set of drives which can maintain higher sustained throughput.
RAIDing a set of drives will actually slow your access speed due to overhead of reading from 2 drives instead of 1.
RAID will speed up your boot time a little, speed up loading times of your games, a little. However, once the game is running, you get more benefit from a single fast drive that is able to access the data quicker, in smaller chunks at a time.
And, with the speed of todays drives, RAID becomes less attractive.
Years ago when drives had very low sustained sustained throughput, like only 20 meg per second, yes a RAID array could make a huge difference. Today, a single decent SATA II drive can easily maintain well over 100 meg per second of transer speed, and some of the better drives can do even close to 150. So RAID 0 is not so much of a benefit as it was a few years ago.
a b G Storage
February 7, 2009 12:06:04 PM

Don't also forget that the failure rate also doubles ... if EITHER drive fails, you loose all. Not as bad as it sounds, but still something to consider...
February 7, 2009 6:16:40 PM

Thanks so much chookman, cjl, 4745454b, jitpublisher and Zenthar for taking the time to write your very informative and learned replies.

I think I was engaged in a little "wishful thinking" in my hopes that a Zero Striped Array would yield a 99% increase in write and access speed.

The hierarchy used to be the CPU "tapping its foot" waiting for data to be transferred to it from RAM via the Front Side Bus. And second, RAM waiting for data to be read off the hard drive. So the CPU wasn't "fed" as quickly as it could be.

But with the very newest Intel multi-core processors coming out which have memory connected directly to the CPU (thus eliminating the need for a Front Side Bus--or any kind of bus), RAM is not as much of a bottleneck as it used to be.

The last remaining bottleneck is storage memory (the venerable 1956 Winchester hard drive).

If so, and if I can get an appreciable speedup from a Zero Striped Array of, say, two drives, I want to do it. (Trouble is, RAID cards cost $800!)

My work involves multimedia work including the Adobe Suite (including Photoshop), video editing, DVD disk creation, Web site design, etc.

Thanx again to everyone,

defender :hello: 
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February 7, 2009 8:51:33 PM

Zenthar said:
Don't also forget that the failure rate also doubles ... if EITHER drive fails, you loose all. Not as bad as it sounds, but still something to consider...


Actually the failure rate is way more than double. If the controller dies, the data is gone. If there's a power outage and no UPS, the data may be gone (happened to me once with an Intel onboard). Turn on the computer and one of the two drives is disconnected? The array will fail and the data might be gone (controller dependent). Most importantly, the data cannot be accessed from another computer by connecting the drives in case of emergency (unless the controller is transported too and supports this).

Bottom line: RAID 0 is great for temporaries and swap files. Other stuff only if willing to loose it or it is backed up frequently.
a b G Storage
February 7, 2009 10:07:42 PM

Quote:
My work involves multimedia work including the Adobe Suite (including Photoshop), video editing, DVD disk creation, Web site design, etc.


So now we know what you use the computer for. As it turns out, you are one of those who can benefit from AID0. I would get a single drive for your OS/data. I would then get 3 or more drives and put them in an AID0 array, or a SSD. On this, put your swap files and other things needed for doing your work. Photo editing isn't to bad, but video editing can use the boost in speed. This of course depends on how much you have to spend. Don't get these if it means you have to drop down from a quad core or something like that.
February 8, 2009 2:17:58 AM

RAID10 would actually be best for what you are doing.

I always run my personal box with RAID0 Raptors for OS, and a second RAID0 array for games and data. Get your stuff setup right and use appropriate bare metal recovery and on-line backup utilities (all free of course) and it only takes an hour or so to recover from a failure. Which won't happen with Raptors (or enterprise SAS drives) unless you mistreat them.

And contrary to what 4745454b says, AID0 isn't a valid technology, it may not be redundant, but it's still called RAID0.
February 13, 2009 3:18:32 PM

rantsky said:
Actually the failure rate is way more than double. If the controller dies, the data is gone. If there's a power outage and no UPS, the data may be gone (happened to me once with an Intel onboard). Turn on the computer and one of the two drives is disconnected? The array will fail and the data might be gone (controller dependent). Most importantly, the data cannot be accessed from another computer by connecting the drives in case of emergency (unless the controller is transported too and supports this).

Bottom line: RAID 0 is great for temporaries and swap files. Other stuff only if willing to loose it or it is backed up frequently.


Thanks for the reply, rantsky.

I thought "Journaling" which Apple stole from BeOS was supposed to take care of what you describe.

I have multiple drives (not RAIDS, though) and have had several power outages. The computer was not shut down properly, the drives weren't parked, and there were no consequences for the drives (except possibly the creation of bad sectors).

defender :hello: 

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