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10,000rpm or RAID ?

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February 10, 2010 6:07:55 AM

Hey guys,

I wanted a quick word of advice, I'm thinking about buying some new storage to replace my current hard drives, would you guys recommend getting one Western Digital VelociRaptor WD3000HLFS 300GB 10000 RPM

or

2 Western Digital Caviar Black WD7501AALS 750GB 7200 RPM and RAID them for extra speed?


I know it's kind of a weird questions, since the second solution obviously comes with more space, but what will the speed difference be?

And what speed will I get if I RAID 2 VelociRaptors together?

More about : 000rpm raid

a c 415 G Storage
February 10, 2010 6:44:24 AM

There are two ways to measure performance, access time (how long it takes to find a file) and transfer rate (how long it takes to read or write the file once you've found it).

For most people, access times are the more important metric because that's what largely determines how fast your system boots and how quickly you can start up applications. This is because these activities have to find a lot of files, but the files aren't particularly big.

A 10,000RPM drive will have a significantly faster access time, but RAID does not improve access time to any noticeable degree.

Therefore, if you're looking to speed up how quickly your system boots and how fast you can launch programs, go for the faster drive.

Actually, if you can afford it you should consider an SSD (Solid State Disk) for the operating system because it blows all of the hard drives out of the water with an access time about 100X faster than a typical hard drive.
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a b G Storage
February 10, 2010 11:04:17 AM

sminlal said:

A 10,000RPM drive will have a significantly faster access time, but RAID does not improve access time to any noticeable degree.

I think Raid0 actually increases access times. The seek times will be twice as fast because the heads are moving shorter distances but the average latency will double because the average latencies of two hard disks have to be added.
Example for a Velociraptor:

Single drive:
Average latency: 3.0ms
Average seek: 4.2ms
Average access: 3.0 + 4.2=7.2ms

In Raid0:
3.0 x 2 + 4.2 / 2 = 6.0 + 2.1 = 8.1ms

But of course this is purely theoretical.
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a c 415 G Storage
February 10, 2010 4:23:46 PM

For RAID 0, the effect depends a lot on the I/O size and the stripe size and whether or not the average read spans more than one stripe, but in general for I/Os that need to be satisfied from both disks then you will have longer access times. If the controller is sensible it will issue the requests in parallel, so you don't really have to add the access times together but you would have to wait for the slowest disk to respond.

For RAID1, a decently smart controller can choose to direct a read request to the drive whose heads are closest to the data, so you can actually get a small improvement in access times.
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February 10, 2010 5:09:27 PM

I have found that RAID-0 of 2 newer high density 7,200 RPM drives makes for a much faster and smoother computing experence than a single 10,000 RPM drive. Now if you RAID some 10,000 RPM drives, they will kick the pants off a RAID of 7,200 RPM drives, but RAID-0 of 7,200 RPM drives is certainly better than a single 10,000 RPM drive.
SSD>>>RAID of either...
Windows DOES boot faster on a RAID-0. Programs DO start faster. The only thing that won't improve much is SEARCH times.
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a c 415 G Storage
February 10, 2010 5:57:39 PM

My experiment with RAID 0 reduced Windows 7 boot time from about 20 seconds to about 18 seconds - a 10% improvement. That's a degree of improvement that you can measure, but which isn't noticeable in real life.
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a b G Storage
February 10, 2010 8:26:25 PM

sminlal said:
For RAID 0, the effect depends a lot on the I/O size and the stripe size and whether or not the average read spans more than one stripe, but in general for I/Os that need to be satisfied from both disks then you will have longer access times. If the controller is sensible it will issue the requests in parallel, so you don't really have to add the access times together but you would have to wait for the slowest disk to respond.

Yes, you are right. If a read operation spans two drives the access time is the slowest access time of the drives.
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February 10, 2010 8:37:12 PM

RAID 0: ideal if you are dealing with extra-large files (video edition, huge data base files etc.).
SSD/Raptors: great if you want to reduce access time (SSD is better, but more expensive).

If you are a gamer: no gain is worth the money. Get a better GPU with money.
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February 11, 2010 12:28:01 AM

Windows was designed, for the most part, to be more friendly to slower drives, as most drives installed are either 5,400 RPM or 7,200 RPM. Startup times are often more dependent on available RAM and processor speed than hard drive throughput. However, when you have a good processor and enough RAM and enough video card power, the last bottleneck in the system is the HDD.
RAID0 for multiple slower HDDs can yield the benefit of making the computing experience more crisp and spiffy.
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a b G Storage
February 11, 2010 2:29:33 AM

Even in slow systems, a fast SSD or HDD can make a world of difference in startup times.
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February 11, 2010 3:31:48 AM

So guys, I just purchased two samsung f3's (500GB) for my home pc (win7) and I'm going to configure them in a RAID setup.

My question is, if I go with RAID 0 should I worry about non-mirroring being an issue? My data gets regularly backed up to a NAS but I feel like in a RAID 0 configuration I'll be walking a tight rope without a safty net. Never done it before.

Also, if I go with a RAID 0 setup with two 500GB drives does that extend the storage out to 1TB or will it still show as 500GB?
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a c 415 G Storage
February 11, 2010 3:46:45 AM

> ...if I go with RAID 0 should I worry about non-mirroring being an issue? My data gets regularly backed up to a NAS but I feel like in a RAID 0 configuration I'll be walking a tight rope without a safty net.

RAID 0 doubles the likelihood of loosing all your data to a drive failure. But it really doesn't matter that much if you have a 2% or a 4% chance - you still need backups. By the way, good backup strategy is to have at least two OFFLINE copies of your data, one of which is OFFSITE. NAS fails both of those criteria.


> Also, if I go with a RAID 0 setup with two 500GB drives does that extend the storage out to 1TB or will it still show as 500GB?

You will have 1TB of usable space. Frankly, if you have to ask that then I have to wonder if you really understand what you're getting yourself into. What do you hope to get out of it?
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February 11, 2010 5:59:36 PM

sminlal said:
> ...if I go with RAID 0 should I worry about non-mirroring being an issue? My data gets regularly backed up to a NAS but I feel like in a RAID 0 configuration I'll be walking a tight rope without a safty net.

RAID 0 doubles the likelihood of loosing all your data to a drive failure. But it really doesn't matter that much if you have a 2% or a 4% chance - you still need backups. By the way, good backup strategy is to have at least two OFFLINE copies of your data, one of which is OFFSITE. NAS fails both of those criteria.


> Also, if I go with a RAID 0 setup with two 500GB drives does that extend the storage out to 1TB or will it still show as 500GB?

You will have 1TB of usable space. Frankly, if you have to ask that then I have to wonder if you really understand what you're getting yourself into. What do you hope to get out of it?


Thanks for the info sminlal. After reading the sticky RAID faq thread I've got more understanding. I'm actually just doing this to "tinker" with my PC. No point really...just for fun.
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