Raid 0 does it help?

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Raid 0 does it help?

Postby Toshi.des » Thu Oct 18, 2007 10:47 pm

well while I'm planning on setting up my HD's in raid 0 because of games and loading windows will it help with the production of videos? :P

Like I know raid improves load times, though I don't know how much, but will it really help me at all with editing videos besides opening premiere faster?

lol if so I think I might buy 4 HD's and put them in raid 0 :P.
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Postby Kariudo » Fri Oct 19, 2007 12:35 am

programs will not run faster if you do raid...but you will be able to write and read data faster.

raid 0 allows for a few milliseconds faster seek...it can add up in applications like video editing where you need to read/write large blocks of data.

raid 0 is for people who want to squeeze every last bit if performance out of their system
here's the results of some HD tach tests that I ran:
generic 250GB Sata drive:
random access: 14.4ms
burst: 121.5 MB/s
avg read: 49.5 MB/s

Western Digital caviar 320GB Sata 3.0GB/s:
random access: 13.0ms
burst: 202.9 MB/s
avg read: 65.9 MB/s

2x WD raptor 36.7GB Sata (10k rpm) in raid 0:
random access: 7.4ms
burst: 121.9 MB/s
avg read: 71.4 MB/s

the burst speed on my raid0 is slower than the 320GB because the raptors are Sata whereas the 320GB is Sata 3.0GB/s (one of the major drawbacks of those raptors...really wish WD would release Sata 3.0GB/s versions)

however there is a drastic increase in random seek, and a fair gain on avg read...I think that you would see an even bigger increase with 4 drives in raid 0, using sata 3.0GB/s would help as well

so if you want to go for it, go for it. Avoid software raid if possible, if your motherboard doesn't have raid support you will either need to get some software raid program or a 3rd party raid card (those ones can be really expensive)
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Postby Willen » Fri Oct 19, 2007 7:05 am

Kariudo wrote:the burst speed on my raid0 is slower than the 320GB because the raptors are Sata 1.5Gbit/s whereas the 320GB is Sata 3.0Gbit/s (one of the major drawbacks of those raptors...really wish WD would release Sata 3.0Gbit/s versions)

Edited for accuracy: small 'b' is for bits, capital 'B' is reserved for byte which is 8 bits.

Maximum PC's November 2007 issue has a nice article on RAID types, advantages, disadvantages, and performance. You should be able to find a copy at your nearest bookstore or newsstand.

Here's an excerpt: (reprinted without permission :o )
HD Tach performance:
Single Drive:

Burst (MB/s): 452.1
Average Read (MB/s): 78.0
Average Write (MB/s): 102.7

RAID 0 (2 Drives):
Burst (MB/s): 358.5
Average Read (MB/s): 156.2
Average Write (MB/s): 158.36

RAID 0 (4 Drives):
Burst (MB/s): 414.1
Average Read (MB/s): 208.7
Average Write (MB/s): 180.2

PCMark05 performance:
Single Drive:

Score: 6,329.0
XP Loading (MB/s): 10.42
App. Loading (MB/s): 4.93
Virus Scanning (MB/s): 77.88
File Writing (MB/s): 160.51

RAID 0 (2 Drives):
Score: 8,949.3
XP Loading (MB/s): 15.80
App. Loading (MB/s): 6.07
Virus Scanning (MB/s): 102.22
File Writing (MB/s): 266.76

RAID 0 (4 Drives):
Score: 11,954.0
XP Loading (MB/s): 23.19
App. Loading (MB/s): 9.07
Virus Scanning (MB/s): 131.52
File Writing (MB/s): 272.87

To sum up, even a 2 drive RAID 0 array will give you an improvement in file reading and writing, OS startup, and program loading. Many PC makers that utilize RAID in their computers do it for the improvement in performance and the fact that the separate physical drives will show up in Windows as a single logical 'drive' (i.e. instead of a 300GB C: and 300GB D:, you see one 600GB C: drive) since Windows puts everything on C: by default and most people never touch their D: until they run out of room (if they even realize that they have another hard drive partition available). The downside is that if one drive fails in a RAID 0 setup, your data is toast regardless if the other drive(s) still work.
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Postby Toshi.des » Sat Oct 20, 2007 1:05 am

I was reading up one what "burst" is for a hard drive :P, from what I've read it seems that the burst transfer rate is the speed of the HD only with information coming from the cache? Where as the avg speed is reading from the platter itself.

Soooo, it's better to buy one with a higher avg reading than burst??? Which would still put the raptor's on top by about 6mb/s?

lol please correct me if I'm wrong cuz I just learned this today. If I'm this information is correct I'll go for a raptor, also doesn't the raptor run at 10,000 rpms? I hear from some that's a noticeable difference from 7200 and from other's that it's not.
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Postby Willen » Sat Oct 20, 2007 8:03 am

Here's what Intel has to say about hard drive burst speeds: http://www.intel.com/support/graphics/sb/CS-010481.htm
Sustained vs. Burst Transfer Rates
Sustained transfers refer to a continued transfer that does not occur from the drive cache. Burst rates refer to data transferred directly to/from the high speed cache. A true indicator of performance is sustained rate; however, most drives are advertised with their faster burst rate.

A typical ATA/100 hard drive bursts at about 100MB/sec from the cache, but has a sustained rate of about 26-42MB/sec, depending on the drive. If you consider a best-case scenario with the 2MB cache full of data, 100MB/sec will quickly deplete the cache and commence transferring at the lower sustained rate.

ATA/66 hard drives are typically less expensive and do not saturate the 66MB/sec bandwidth available. In fact, a hard drive with a sustained transfer rate of 26MB/sec will not even saturate available ATA/33 bandwidth.

In summary, sustained transfer rates should be considered over burst transfer rates for maximum hard drive performance.

The average read (sustained transfer) rate is more important, especially when dealing with larger files. Generally, larger cache memory sizes will give you higher burst transfer speeds. This is one of the reasons why the older Raptors may lose out in burst speed comparisons. 1st gen 36GB Raptors had 8MB caches in addition to their SATA 1.5Gbit/s interfaces. Later ones upped the cache to 16MB, but the SATA interface is unchanged, so compared to other 16MB cache drives with SATA 3.0Gbit/s interfaces they still have a disadvantage. But, as stated above, burst speeds aren't the most important spec to look at.

See the random access numbers? That's due to the fact that the Raptors use a 10,000 rpm rotational speed. Raptors can find data on their platters quicker due to that advantage. Their downside is their cost per GB, not to mention they top out at 150GB in capacity when 1TB (Terabyte or 1000GB) 7,200 rpm drives are available.

Now, here's a chart comparing average transfer (read) rates: http://www23.tomshardware.com/storage.h ... 0&chart=34

You may also wonder why the 10,000 rpm Raptor's average read speeds aren't much better than a 7,200 rpm drive's. If the platter is moving faster under the heads, data should be being read off the drive faster also, right? The reason is partly due to lowlier drive having higher density platters. Since these high capacity drives achieve their gains by packing bits closer together, the same segment of platter area of a 1TB drive contains much more data than the equivalent segment of a Raptor's platter. So why doesn't Western Digital combine these high capacity platters and 10,000 rpm motors for the best of both worlds? I don't know (although I can speculate).

If cost isn't an object, Raptors in RAID 0 is still the best performing setup overall. Personally, I use a RAID 0 setup with 2 WD Caviar SE16 WD2500KS drives for my data storage (which is most of my video files).

BTW, the MaximumPC article used WD Raptor drives in all the tests.
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