braddeicide

Effect of platter count

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I'm looking at Western Digital RE4's, I was about to buy 4x2Tb for raid but I found a few places where people cryptically said less platters = faster. These drives are for OS+storage so that's an issue. I've been trying to find benchmarks that compare drives in the same series of different sizes to see what kind of effect it has, but I can't find any. Does anyone know more?

I've considered that If I did get 2Tb drives and partition the first 500G for OS/Programs then that would have the same effect as short stroking and would be faster than a 500G drive, as long as storage partitions weren't accessed at same time. Jeez I wish someone would just give me access to a bunch of hdds to test stuff on ;)

Edited by braddeicide

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Fewer platters means higher sequential transfer rates (STR) if the capacity is similar, i.e. what they actually want to say is: platters with higher density provide higher STR (if the platter size is similar, i.e. don't compare 3.5" vs. 2.5"). And you're right: a smaller parition at the beginning of the drive brings the same benfits as short stroking. The remaining part can be used for bulk storage.

Notice how I only talked about STR. Random access time and therefore random performance is a different beast. It may actually suffer if you use denser platters, as the tracks become so small that the drive needs longer (on average) to find them. You can see the effect in the recent Samsung F4 review: it uses a half 640 GB platter at 7.2k rpm (a record, as far as I know) and thereby achieves amazing STR. Access time however isn't very good (admittedly, the Blacks are really tough competition). Even more illustrative is maximum latency: the 640 GB platter F4 is worst, followed by the 500 GB platter 2TB Black (which even uses a 2-stage actuator to reduce this problem). And both are easily beaten by the 500 GB 3.5" Black, which uses 2 mature 250 GB platters.

Regarding your specific question about 4x2 TB drives: which drive category are you looking at, performance or green? If performance then the 2 TB Black is your obvious choice. It won't come cheap, though. Regarding Green (5k rpm) drives I'd go with the 'Cuda LP for it's higher rpms or the WD Green for its better firmware. There's also the option to go with the Hitachi 5 platter 7.2k rpm drive, which is much less expensive than the 4 platter 7.2k rpm 2TB drives. It's louder and hotter, though. Otherwise at 2 TB platter count really doesn't matter, because apart from the Hitachi your only choice are 4 x 500 GB platters. The only question remaining is whether they should be 5 or 7k rpm. If you're looking at 4 of the WD Blacks I'd suggest going for Cuda LPs instead and investing the money saved into a Sandforce SSD for system and common programs. Your choice - I don't know what you're storing there. I know capacity would be fine for me.. but then I'm currently using a single 640 GB drive ;)

MrS

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Thanks for reply MrSpadge,

So platter count doesn't matter towards performance other than as an indicator of density? Density is the performance changer.

I wonder if this over-density is why Western Digital is still advertising RE3 despite RE4 being availible.

I did consider a slow/fast split, but i'm still not keen on the disadvantages of SSD, so I decided on good performance classic hdds. I only upgrade every 5 years so yeh I don't skimp, and i've had raid card imcompatiblities before so I like to buy a product aimed at raid so maybe the hdd vendor will be more co-operative with raid vendors than maxtor was :). And I havn't had a Hitachi since the faulty designed 75gxp. Do I carry grudges too long? :)

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The enterprise drives have a much longer life, you'll see the previous generation for years sometimes to support those who have standardized on a particular drive. So with the RE4 being relatively new, I'd expect to see the RE3 around for a while still.

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MrSpadge' date='02 October 2010 - 11:35 AM' timestamp='1286015735' post='264499']...Otherwise at 2 TB platter count really doesn't matter, because apart from the Hitachi your only choice are 4 x 500 GB platters. ...

MrS

The latest WD20EARS I bought, manufactured Aug15, was with only 3 platters. No reinforced lid or screw in the middle of the lid, and higher sequential speeds. Just wanted to point that out. :)

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Thanks MultiMan. Almost funny: just after writing that post I got a newsletter saying they'd be testing a 3 platter WD20EARS. The link didn't work, though. What Maximum STR do you get from that drive? Does it use 4k sectors?

MrS

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I wonder if this over-density is why Western Digital is still advertising RE3 despite RE4 being availible.

The RE4 (non-GP) was announced over a year ago with great fanfare, yet availability of the drives are still spotty at best.

I've been wondering if WD is having problems manufacturing them.

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