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SATA 6 @ 7.2k rpm or SATA 3 @10k rpm

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June 8, 2010 2:48:47 PM

Hi,

I was wondering if anyone has tested the REAL performance gains from SATA 6 controllers and drives such as:

- Western Digital Caviar Black 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive (p/n WD1002FAEX)

versus ...

- Western Digital VelociRaptor 300GB 10000 RPM 16MB Cache SATA 3.0Gb/s 3.5" (p/n WD3000BLFS or WD3000HLFS)

Also ... would you consider doing RAID 0 for a Workstation used for processing digital content with programs such as Photoshop, Premiere, etc.?

Thanks!

More about : sata rpm sata 10k rpm

a c 127 G Storage
June 8, 2010 4:29:34 PM

You could be connecting those to SATA 1.5Gbps and see no real difference. The SATA 6Gbps is only intended for new SSDs that come out around christmas. It has no relevance for harddrives; as they reach below 150MB/s the speed limit of SATA1; SATA2 or SATA/300 has 300MB/s of bandwidth; much more than the HDD can transfer.

So forget the SATA speed; it is irrelevant. You are comparing the Velociraptor 300GB (the older version) to a regular 1TB 7200rpm disk. As a system disk, an SSD is still hundreds of times better.

You can best store your:

system disk data: on SSD
large files (movies/archives): on 5400rpm drives ( the lower the rpm; the better )
small files (games/apps): on SSD or on 10k RPM HDDs (velociraptor)
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June 8, 2010 6:20:44 PM

sub mesa said:
You could be connecting those to SATA 1.5Gbps and see no real difference. The SATA 6Gbps is only intended for new SSDs that come out around christmas. It has no relevance for harddrives; as they reach below 150MB/s the speed limit of SATA1; SATA2 or SATA/300 has 300MB/s of bandwidth; much more than the HDD can transfer.

So forget the SATA speed; it is irrelevant. You are comparing the Velociraptor 300GB (the older version) to a regular 1TB 7200rpm disk. As a system disk, an SSD is still hundreds of times better.

You can best store your:

system disk data: on SSD
large files (movies/archives): on 5400rpm drives ( the lower the rpm; the better )
small files (games/apps): on SSD or on 10k RPM HDDs (velociraptor)



Very interesting, I didn't consider the fact that my tests on the SATA6 drive (connected to a SATA6 adapter) still gave me transfer rates below 300MB/s ... better performance than my Seagate 1TB 7.2k but not even close to what should be expected.

I have to say that I'm intrigued by your comment regarding "lower the rpm; the better" ... could you explain?

Thanks!
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a c 127 G Storage
June 8, 2010 9:02:28 PM

Harddrives can not read or write higher than 150MB/s. The only thing that goes higher, is burst speeds which is to the cache chip. That's rather useless, as its much smaller than your 4GB RAM which also acts as cache.

HDDs don't need much cache memory; they need about 1 or 2 MB to allow them to do 'write-back'; that means they store all write requests the HDD receives to its memory chip instead; so it builds up a queue of write requests to do. This 'queue' makes sure the mechanical part of your harddrive can continue to work.

Thus, any more cache memory is mostly marketing. The benefit is extremely low; cache on your CPU now THATs important but not on your HDD. Don't trick yourself by the marketing!

So HDDs do about 100-140MB/s; SATA/300 is more than enough for those. Even SATA/150 wouldn't limit their speed to any noticeable degree.

Now the RPM part, which is more difficult:

low rpm, high density (2TB 5400rpm): bad as system disk (random access) - good for large files (throughput)

high rpm, low density (300GB Velociraptor 10.000rpm): good as system disk (random access) - worse for large files (throughput)

As you can see, the 10K rpm Velociraptor isn't that good for storing large files; such as movies, music, archives, whatever. It could be even slower than a 5400rpm disk; how can that be? Well, higher rpm does mean higher performance; but only if all other factors remain the same. That's not the case with the Velociraptior, as its data density is less high than the 500GB/platter 5400/7200rpm harddrives out now.

Platter density is probably the most important spec for a harddrive; you could instantly see how 'advanced' the drive is and to which generation a HDD belongs by looking at its density. HDD makers don't make it easy to find this; it's buried in the specs. For example:

500GB/platter: current generation
333GB/platter: previous generation (still being sold)
250GB/platter: old generation (still being sold for disks 500GB and below)
200GB/platter: etc..

So the primary specs to look at are:

1. Platter density (2TB should be 4 x 500GB platters = 2000GB)
2. rotation speed (5400rpm best for: large files; 7200/10.000: random access)
3. Sector size (512 = default; 4K means Advanced Format drive which could be more reliable but requires aligned partitions; not suitable to Windows XP)

That's it really, forget the SATA generation, forget the cache chip size.

I said 'the lower the rpm, the better' since lower rpm means lower power consumption; less heat. And still good data throughput. The access times will suffer though; so a low rpm HDD would be a terrible system disk; but still a good mass-storage disk for large files. 7200rpm disks require cooling and have lower lifetime due to them rarely being cooled properly.

Temperature is not that important to HDDs; it is temperature variation that kills HDDs; one part being cooled while the other not could create an imbalance; and quick temperature changes are what wears on a HDD. It will contract and expand the metal inside the HDD tearing it apart over time. That's why i recommend 5400rpm disks; you don't need to cool them and because of that will have very modest temperature changes and perfect heat spread over the surface because you're not actively cooling them; heat will travel uniformly and dissipate slowly.

Sorry for the long message; but hey you don't read this info everywhere. Some may argue some points i made; but i think this pretty much sums it up in an understandable way.
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a c 143 G Storage
June 8, 2010 9:17:04 PM

^+1... Well said!!! :) 
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a c 114 G Storage
June 8, 2010 9:47:52 PM

Well, you have to consider what a Hard Drive does.....there are two types of transfers from a HD:

1. Transfers from data read off the disk as it spins.....obviously the 10k drive, all things being equal such as areal density, etc) will be faster here. Note that a 7200 rpm drive with a 500 GB platter will have a theoretical equivalent speed, again all things being equal, of a 10k driver w/ a 360 GB platter

2. Transfers from cache ..... with today's larger cache's you'd be surprised at the amount of I/O results from cache transfers. For transfers from cache, the SATA III (6 GB/s), 7200 rm drive will be faster.
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a c 127 G Storage
June 8, 2010 10:03:03 PM

Transfers from cache are rare in the real world. That's because it can only be in the cache if the HDD has read it before. In that case, would you read it again then yes you would be reading from cache. But with 4GB RAM your RAM cache is a lot bigger than your 32/64MB HDD cache; which also gets used for write back; so it's a buffercache.

Due to your filesystem already caching everything it reads in your RAM, until the RAM runs out and it overflows; killing cached older data. So normally, your RAM should speed up things a lot because read requests will be handled directly by the RAM not having to wait for your terribly slow disk. For one seek alone (10ms) you do about 30 million CPU cycles; just to keep things in perspective.

In some synthetic benchmarks the effects of cache chip could be huge, but i would argue the real-world effect is too small; compared to the bigger benefits of having a 750GB-per-platter harddrive. But hey that costs the HDD makers a lot of money to research; just putting a 128MB memory chip might make it sell crazy. And yes SATA 6Gbps makes this a killer product!

And they are right; marketing sells. But ultimately, if you're looking for smart buys that focus on the technical/scientific story only; you would be looking at different specs instead.

I would make one reservation; if you would have a large array; having a lot of cache adds up nicely; 128MB per drive in a 16 drive configuration is already 2GB. Yes then it starts being useful. But still i would rather have 2GB extra RAM; RAM is so useful as filecache.
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June 9, 2010 2:51:39 AM

Best answer selected by rodmanlab.
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June 9, 2010 2:55:30 AM

I have not been able to find the density info on the WD1002FAEX SATA6 HDD, I would really like to read Western Digital's design.

Thanks for the information sub mesa, I am very impressed with the fact that this whole bla bla about SATA 6 is not really doing much for us ... at least today.

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July 4, 2010 2:21:21 PM

sub mesa said:
Transfers from cache are rare in the real world. That's because it can only be in the cache if the HDD has read it before. In that case, would you read it again then yes you would be reading from cache. But with 4GB RAM your RAM cache is a lot bigger than your 32/64MB HDD cache; which also gets used for write back; so it's a buffercache.

Due to your filesystem already caching everything it reads in your RAM, until the RAM runs out and it overflows; killing cached older data. So normally, your RAM should speed up things a lot because read requests will be handled directly by the RAM not having to wait for your terribly slow disk. For one seek alone (10ms) you do about 30 million CPU cycles; just to keep things in perspective.

In some synthetic benchmarks the effects of cache chip could be huge, but i would argue the real-world effect is too small; compared to the bigger benefits of having a 750GB-per-platter harddrive. But hey that costs the HDD makers a lot of money to research; just putting a 128MB memory chip might make it sell crazy. And yes SATA 6Gbps makes this a killer product!

And they are right; marketing sells. But ultimately, if you're looking for smart buys that focus on the technical/scientific story only; you would be looking at different specs instead.

I would make one reservation; if you would have a large array; having a lot of cache adds up nicely; 128MB per drive in a 16 drive configuration is already 2GB. Yes then it starts being useful. But still i would rather have 2GB extra RAM; RAM is so useful as filecache.


Well, I am interested cnet just tested the new 10000 rpm with larger cash and give it some rave Deskstar E7K1000 as a system drive. What is your opinion on this new drive. And your mention of 6 coming out soon, next year will that mean new motherboard to use it effectively for system drive on raid. I have win 7 i7 with 6 gb ram, and a 6 tb array, but my scores are all over 7 except for the 5.9 on the system hardrive is the only low score with my ati radeon 5970 which really does what is advertised since it comes with redline to overclock it a small bit. Tell me your considered opinion please. You are so correct on your tech. Tell me about the new 10000 rpm hdd deskstar tested by engadget also. thankyou very much. miker3x
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