Linked by Thom Holwerda on Thu 27th Sep 2012 19:36 UTC
Apple I bought a brand new iMac on Tuesday. I'm pretty sure this will come as a surprise to some, so I figured I might as well offer some background information about this choice - maybe it'll help other people who are also pondering what to buy as their next computer.
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WereCatf
Member since:
2006-02-15

Regarding swap, realistically no high performance rig should use it. Get enough ram and be done with it. The only time memory should be stored to disk is for hibernation.


If you have enough RAM in the system then it doesn't really matter where the swap is as it will mostly go unused anyways. There may be a write here or there occasionally, but atleast on my rig those are very few.

And in the case of hibernation, it's one big linear read/write with no seeking overhead. If it's placed on the outer rim of the disk, this is peak performing scenario for HDD, so I'm not even sure if the hibernation file benefits from SDD. Anyone have performance data on this?


Hibernation files are indeed big linear chunks of data, but performance-wise SSDs still win out: any modern SSD can easily do 500MB/s sequential read and atleast 200MB/s sequential writes, whereas atleast my own HDDs barely manage 100MB/s sequential reads and 60MB/s sequential writes in optimal case -- this with 3.5" desktop HDDs, my 2.5" ones fare even worse. I can post screenshots from HDTune Pro if needed, but e.g. my laptop's 500GB drive starts at 75MB/s sequential read speed at the furthest edge of the platter and drops all the way to around 50MB/s sequential read when closest to the center of the platter.

So yes, you'll still boot up much faster with an SSD.

Now, if boot times aren't as important to you, ie. only actual runtime - performance matters, then it would make sense to slap hibernation files on the HDD instead. In my own case I usually boot my PC 1-3 times a day so it's not really a whole lot of time wasted even if I had to wait 3 seconds longer every boot -- I usually pop to kitchen and grab a drink anyways while the system is booting. In other words I wouldn't benefit much from placing hibernation files on the SSD.

Reply Parent Score: 3

Alfman Member since:
2011-01-28

WereCatf,

"I can post screenshots from HDTune Pro if needed, but e.g. my laptop's 500GB drive starts at 75MB/s sequential read speed at the furthest edge of the platter and drops all the way to around 50MB/s sequential read when closest to the center of the platter."

Well, you're talking laptop drives, which are often much slower than desktop equivalents due to much slower 5400RPM and a much smaller platter at the rim such that fewer bits fly under the heads per rotation. Your conclusion is absolutely true. However I was wondering about a HDD rig built for performance.

I have to admit thought that 500MB/s seems hard to beat, heck I don't think my (bargin priced) motherboard could even support that data rate.

Reply Parent Score: 2

WereCatf Member since:
2006-02-15

Well, you're talking laptop drives, which are often much slower than desktop equivalents due to much slower 5400RPM and a much smaller platter at the rim such that fewer bits fly under the heads per rotation. Your conclusion is absolutely true. However I was wondering about a HDD rig built for performance.


Well, the desktop drives I have are in striped RAID so the values reported by HDtune Pro are reflective of that. I still decided to run a benchmark for you, they still show what they need to although transfer rate reported is higher than it would otherwise be. These are 7200RPM 3.5" drives. Also, these are in use in the sense that my Windows - installation resides on them. I did kill all unnecessary background - processes, though, and let the system idle for a while before starting the benchmark.

First, I did two runs with the stroke - option on, ie. I limited the benchmark to the 8 gigabytes of outermost edge of the platters:
http://dl.dropbox.com/u/11811685/stripe1.png
http://dl.dropbox.com/u/11811685/stripe2.png

Then I disabled stroke and let it do the whole thing through:
http://dl.dropbox.com/u/11811685/stripe3.png

As you can see the seek times are consistent with what they should be for a 7200RPM drive and the graph shows quite nicely how transfer rates drop the closer to the center of the platters you go while seek times rise. On a non-RAID setup this would be much sharper, though, do keep that in mind! Also, as you can see even with two 7200RPM drives in striped RAID the system barely manages 200MB/s.

Does this answer your question? Also, I expect atleast a thank you :/

I have to admit thought that 500MB/s seems hard to beat, heck I don't think my (bargin priced) motherboard could even support that data rate.


SATA II supports up to around 300MB/s, SATA III is required for the 500MB/s+ speeds.

See https://en.wikipedia.org/wiki/Serial_ATA#Revisions

Reply Parent Score: 2