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Why buy a 10k RPM HDD instead of RAID two 7.2k's?

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September 19, 2007 2:17:10 AM

I'm no smarty pants, but I noticed the latency and seek times for the 10k RPM hard drives are just shy of half of what the 7200 RPM ones are. Now, I'm not sure of what the actual performance boost is of running RAID 0..... but in theory it should be about double the speed. (Two drives, each taking half the data) So why spend out the wazoo for a 10k RPM HDD when you could just buy two 7,200RPM ones and run them in RAID 0? You'll pay less and get more storage. Hell... you could probably run three 7,200 RPM drives in RAID 0 for the $140 a 10k drives costs.

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September 19, 2007 2:45:08 AM

RAID 0 improves only the sequential transfer rate of the array (i.e. if a single drive does 70 MB/sec, a RAID 0 array comprised of two of those drives can potentially do 140 MB/sec, barring other items that may cap the transfer rate, such as interface limits). RAID 0 does not improve the seek, latency, or total access times to the data (in fact, it slows them down).

The net effect of RAID 0 vs. 10K RPM is highly application dependent. Some applications are well suited to a RAID 0 array with its high sequential transfer rates (video editing, DVD authoring, Photoshop scratch disks -- anything that works with huge files). Other applications are much better suited to the low seek, latency, and access to data times of a 10K RPM drive (databases, web servers, e-mail servers -- anything that needs random access to many small files or many small blocks of data).
September 19, 2007 2:57:28 AM

Ahh, making some sense. I partially understand. I see that the actual read/write speed of each drive may not change... but each drive only has to do half of the file....? It may still be at a slower seek and latency rate, but it only has to do half the work? Giving the user an end result of double speed...? I know I'm wrong, but please help me understand a little better.
September 19, 2007 3:11:44 AM

Indeed. A raid 0 solution stripes the data to both drives. When it reads back the data it pulls the data from both which increased read and write speeds. It doesn't effect the latency, seek, and access times.

this is why people still buy raptors. They may be older technology since they don't run PMR. But their rotation speed makes up for it. If they ever end up doing a refresher with the current hard drive technology it would get even better. Hopefully that'll happen sooner or later..=(
September 19, 2007 4:18:43 AM

Kamrooz said:
Indeed. A raid 0 solution stripes the data to both drives. When it reads back the data it pulls the data from both which increased read and write speeds. It doesn't effect the latency, seek, and access times.
I realize RAID 0 will not affect the actual seek times of the drives.....Obviously all I care about is the end result.
September 19, 2007 4:54:58 AM

firebirdude said:
I realize RAID 0 will not affect the actual seek times of the drives.....Obviously all I care about is the end result.
Whatever that means.

You have gotten a complete answer there is really no more to add, except that you are at a much greater risk of loosing all of your data.

What you might want to do is research the terms that were used in the explanation, that you said you understood. And, maybe read some drive reviews, in order to get a full understanding how all of the various terms e.g., latency, seek, etc. etc. interact to determine the true speed of a drive, based on the type of usage. Then do the same with RAID0. Then maybe read some articles on comparing stand alone drives against RAID. Then and only then will you understand. If you need me to compile the information and present you with the links just ask.
September 19, 2007 1:51:26 PM

Zorg said:
Whatever that means.
It just means that I realize the actual drive speed will not change. They can only do what their rated to no matter what. But I figured the more of those drives (7.2k) I have, the more sections the data can be split. Each drive my still read/write slow, but they have less data to transfer. Thereby giving me the end result of a faster load.

I've read a few articles now and see exactly what SomeJoe mentioned. Once in awhile, the RAID 0 is actually faster than the single Raptor. But most of the time, the Raptor was the winner. I will most likely follow the well beaten path of getting a single 10k small size drive to install my games etc on and a huge massive 7200 drive for general storage.

Oh and I found this link helpful for anyone reading this that might need more info.
http://www.anandtech.com/storage/showdoc.aspx?i=3087
Be sure to read the conclusion. That really ties it up. Thanks!
September 19, 2007 3:04:47 PM

Raid 0 is better for large files like video encoding
10k rpm is better for small files like what games access while playing.
September 19, 2007 3:46:39 PM

Lets put it another way... a Raid0 array using 7200rpm drives can transfer data faster than a single 10000rpm Raptor. HOWEVER, before the data gets transferred it must be FOUND. And that is where the faster seek time of the Raptor comes into play. The Raptor will be MUCH faster locating the data.

So if you are working with really large audio or video files then the 7200rpm Raid0 array will take longer to locate them but pull ahead when it starts to read them because there is so much data. Whereas the Raptor will find the files faster but be slower reading them once they are found.

Now for most applications and your OS the files are typically pretty small and scattered around the disk. So the seek times of the Raptor will be superior here because it will find the files and read them before the 7200rpm Raid0 array even has them located.

To get the best of both worlds you can do what I did... just setup a Raid0 array with 2 Raptors! ;-)





September 19, 2007 3:57:16 PM

What's better for gaming:

a) 10k RPM Raptor

or

b) two 7200rpm drives, one with OS and one with games (both on the outer edge partitions)

?
September 19, 2007 4:09:11 PM

10k raptor
September 19, 2007 4:15:35 PM

In my opinion, the Raptor is better for gaming.

Or you could try a thrid option. My new build has a 150gb Raptor for a C: drive and a 250gb Seagate for a D: drive to store data. If I fill the 250gb Seagate, I can add another one, or buy a larger drive and use it as a D: drive.
September 19, 2007 5:11:23 PM

I wonder why they dont build drives with RAID0 built in. Sorta like dual channel memory controllers? With mass production it would have to be cheaper than two physically separate drives.
September 19, 2007 5:12:49 PM

There's multiple options. The one I went with is:

2x 74GB Raptors in RAID 0 for the OS and applications and some games (64K stripe)

2x 250GB WD250GB's in RAID 0 (128K stripe) for audio editing, photoshop playing, general data, and virtualization

1x 500GB that meaningful from both arrays is backed up to.

...not the best solution but not too terrible either, its responsive enough.
September 19, 2007 5:13:01 PM

There's multiple options. The one I went with is:

2x 74GB Raptors in RAID 0 for the OS and applications and some games (64K stripe)

2x 250GB WD250GB's in RAID 0 (128K stripe) for audio editing, photoshop playing, general data, and virtualization

1x 500GB that meaningful from both arrays is backed up to.

...not the best solution but not too terrible either, its responsive enough.
!