Personal computing discussed
Moderators: renee, morphine, Steel
Nec_V20 wrote:I ran the test through three times in each configuration and I have noted the best result I got out of three for each.
just brew it! wrote:Nec_V20 wrote:I ran the test through three times in each configuration and I have noted the best result I got out of three for each.
Why did you pick the best of three in each case? I would be a lot more interested in seeing the average of each set of three. That's probably a better indication of true performance since it filters out more of the normal variation you'll see from run to run due to measurement slop. I'm not questioning your original hypothesis (it makes sense to me); I just think your measurement methodology leaves something to be desired.
In systems with more than one drive you've got another variable: vibrations transmitted between the drives. While this will be smaller than the vibrations from a drive's own head actuator, it could still be significant since no case is perfectly rigid. As you add more drives, there may even be a point at which the "squishy" mounts become a net win because they help isolate a drive from the vibrations of its neighbors.
Chrispy_ wrote:Given the negligible performance gains, plus the fact that pretty much everyone would rather be using solid-state drives for their OS these days, I see no reason to ever make your entire case resonate as a giant sounding box by rigidly attaching it to a disk.
Decoupling/damping the drives has been the more desirable feature for over a decade and when you think about rigidly fixing two drives to a cage, the vibrations of one drive will actually throw off the heads on the second drive more if they are both rigidly mounted. If you were interested in testing this, I'd be curious to see how a pair of drives softmounted/hardmounted perform when benchmarked simultaneously.
Nec_V20 wrote:That was plain and simply because if I had taken the average then the results would be even further apart. The tests done when the drive was in the caddy without the screws were a lot further apart than the ones I did when the drive was affixed with the two screws, so the result would have been crasser.
Nec_V20 wrote:I doubt very much that any hypothetical harmonics transferred to the casing from another drive would change the results in any significant way.
Western Digital wrote:Rotary Acceleration Feed Forward (RAFF)
Information Sheet
Rotational Vibration Cancellation Technology in WD Enterprise Hard Drives
...
RV is induced in a hard drive as a result of other drives' spinning and seeking in the same chassis.
mac_h8r1 wrote:Having taken apart several hard drives, the voice coil and arm seem to be pretty well balanced. The only force applied to the drive chassis itself is by the voice coil, and is thus parallel to the spinning moment of the discs. The discs are FAR heavier, and even at 5900RPM are moving INCREDIBLY fast (ever lift a non-mounted hard drive? you can balance it on your finger due to the gyroscopic physics at work). I just don't see the voice coil putting enough energy in to the drive to add enough mechanical noise to be a problem.
Nec_V20 wrote:Who said I was using the 4 TB drive for my OS?
Nec_V20 wrote:The only reason why they do that is because people were whining about the hard drives being too noisy
Nec_V20 wrote:and they didn't know "lefty loosey, righty tighty"
Nec_V20 wrote:And if you don't know that then you haven't been in the game all that long.
Nec_V20 wrote:The effect of one HD on another would be negligible unless you have a REALLY flimsy HD cage and even then the effect would not be of the order of over 0.4ms. You know what, you can believe the other posters old wives tale if you want, it's no skin off my nose.
Just sit back and actually THINK about what you are trying to tell me here!
Nec_V20 wrote:Now I did the work and gave you and just brew it! the results. If you think that more drives would interfere THAT MUCH then do the experiment and get back to me with the results.
just brew it! wrote:Nec_V20 wrote:I ran the test through three times in each configuration and I have noted the best result I got out of three for each.
Why did you pick the best of three in each case? I would be a lot more interested in seeing the average of each set of three. That's probably a better indication of true performance since it filters out more of the normal variation you'll see from run to run due to measurement slop. I'm not questioning your original hypothesis (it makes sense to me); I just think your measurement methodology leaves something to be desired.
Erm... wait a sec. So you intentionally cherry-picked results that show only a 3% difference (i.e. nowhere near statistically significant, given that you've just indicated that the results are varying all over the place), thereby undermining the very point you're trying to make?
So RAID/enterprise class drives that implement vibration compensation (also known as RAFF) are snake oil?
Rotary Acceleration Feed Forward (RAFF) overcomes the
effects of RV [Rotational Vibration] on a hard drive by sensing RV disturbance and
controlling head position to keep the drive heads within the safe
operating region during read and write operations
RV is induced in a hard drive as a result of other drives'
spinning and seeking in the same chassis. RV can also be
induced by external forces on the rack or chassis containing the
hard drives. Even linear vibrations applied on a chassis may get
converted to RV at the drive level if a chassis is not designed
appropriately. An example of this would be a drive bay structure
that is not rigidly attached to a chassis.
Nec_V20 wrote:Now as you can clearly see the concept of RAFF has nothing to do with the access time I alluded to in my original post, but rather to keep the heads over the track whilst reading/writing is taking place. So you are comparing apples and oranges and declaring them equal.
Chrispy_ wrote:Man, I don't know where you've sprung up from but a lot of your replies to other people seem to be argumentative, malicious or irrationally-defensive based on your assumptions of what you think other person is implying rather than the hard facts of what they have actually written.Nec_V20 wrote:Who said I was using the 4 TB drive for my OS?
Not me. The reason I mentioned it at all is because the OS itself is typically the most seek-intensive thing a mechanical hard drive needs to do these days, and generalising, the trend is towards the OS being on an SSD and mechanical being used for low-IOPS media storage with minimal seeking.Nec_V20 wrote:The only reason why they do that is because people were whining about the hard drives being too noisy
Well, yeah. There's a multi-million dollar industry sector dedicated to making everything quieter; typically if you look at independent professional reviews, as well as user reviews you'll typically see "too loud" and "noisy" listed as negative points that reduces the value of the item in question. Loud is bad, mmmkay?Nec_V20 wrote:and they didn't know "lefty loosey, righty tighty"
I guarantee you that the tightening the hard drive mounting screws will cause the setup to generate more noise than leaving them loose (which is effectively partial-decoupling). If you don't understand that then you need to read up on the theory of acoustic resonance, I'm not going to re-explain what is easily Googled.Nec_V20 wrote:And if you don't know that then you haven't been in the game all that long.
See above, and my opening sentence. There's no need to take this kind of stance and it just makes you look bad for veiling an insult with patronism. If you were unquestionably right (which you definitely are not), being patronising is still considered an abrasive attitude trait that polite society frowns upon; Fortunately I'm not particularly polite (I prefer blunt, brutal honesty) so anything I say is mildly hypocritical and I'm not going to waste effort frowning upon you.Nec_V20 wrote:The effect of one HD on another would be negligible unless you have a REALLY flimsy HD cage and even then the effect would not be of the order of over 0.4ms. You know what, you can believe the other posters old wives tale if you want, it's no skin off my nose.
Just sit back and actually THINK about what you are trying to tell me here!
Uh, really? Well for a start, I'm not telling you anything you haven't already suggested yourself - which is that drive arms seeking cause significant vibration and failing to secure this vibration slows down the seeks. I'm suggesting that if a single drive is improved by reducing its own vibrations, then it may also be hindered when introduced to vibrations transmitted through a drive cage by other drives. This is why I say "I'd be curious to see them benchmarked simultaneously" because I don't know for sure and have no empirical data oooh, now I do - notfred has given me some!
Anecdotally, enterprise drives incorporate accelerometers to help counteract the foreign vibrations caused by other drives in the same rack, the fact these are expensive and complex upgrades seems to indicate that these vibrations are more than trivial and it is worth significant investment to counter them.Nec_V20 wrote:Now I did the work and gave you and just brew it! the results. If you think that more drives would interfere THAT MUCH then do the experiment and get back to me with the results.
Well, it's your experiment and you publicly published the results which are free for criticism and comment.If you can't take constructive criticism well, then you probably shouldn't publicly publish your work. This is the internet, after all - if you don't know that then you haven't been in the game all that long
- JBI queried your rather unusual method of cherry picking the best results
- I implied that the experiment is only valid for one drive (with reasons) and that further testing could show if the results apply to multiple drives or not.
Nec_V20 wrote:JBI's "criticism" was both statistically and factually unfounded and I replied to both of those above. You jumped in assuming that JBI had his facts straight and proceeded to use that as the basis for criticising my original post.
It was your blind premise "JBI must be right therefore Nec_V20 must be wrong" attitude which irked me.
This is not by any stretch of the imagination "constructive criticism", but rather, given the amount of time and posts you have both have shared here, a case of "incestuous amplification".
Captain Ned wrote:Nec_V20 wrote:Now as you can clearly see the concept of RAFF has nothing to do with the access time I alluded to in my original post, but rather to keep the heads over the track whilst reading/writing is taking place. So you are comparing apples and oranges and declaring them equal.
Average the times of several test runs for both conditions and we'll talk. If you read the "how did we do this" section in any review posted by Damage, Dissonance, or Cyril you'll see that all test results are averages of multiple runs. Do the work, work to the standards of TR reviewers, and no one will give you crap for your testing methods.
Captain Ned wrote:Nec_V20 wrote:JBI's "criticism" was both statistically and factually unfounded and I replied to both of those above. You jumped in assuming that JBI had his facts straight and proceeded to use that as the basis for criticising my original post.
It was your blind premise "JBI must be right therefore Nec_V20 must be wrong" attitude which irked me.
This is not by any stretch of the imagination "constructive criticism", but rather, given the amount of time and posts you have both have shared here, a case of "incestuous amplification".
Do you really want to double down on being wrong? Follow the TR testing procedures stated in every review and get back to us.
Captain Ned wrote:Nec_V20 wrote:JBI's "criticism" was both statistically and factually unfounded and I replied to both of those above. You jumped in assuming that JBI had his facts straight and proceeded to use that as the basis for criticising my original post.
It was your blind premise "JBI must be right therefore Nec_V20 must be wrong" attitude which irked me.
This is not by any stretch of the imagination "constructive criticism", but rather, given the amount of time and posts you have both have shared here, a case of "incestuous amplification".
Do you really want to double down on being wrong? Follow the TR testing procedures stated in every review and get back to us.
Airmantharp wrote:Without accusing him of anything, please note that the bar for 'statistics' here is set rather high.
If someone wants to do some independent testing and be taken seriously, they'll need to submit to intense scrutiny. All of the other extraneous BS that Nec_V20 has brought to this thread and this forum has done enough to discredit his results, and I think that forum members that have asked him to follow standard TR testing procedures are being completely fair. It's not personal, even though he's gone out of his way to deserve it.
Nec_V20 wrote:I spoke originally of "results" not "statistics" in my original post.
And personally I know techies when I meet them and so far what has confronted me here on this thread is wannabe's with a ton of probably less rather than more valuable posts on the MB.
So don't try to pile on, you just make yourself look bad by association.
Nec_V20 wrote:... Now as you can clearly see the concept of RAFF has nothing to do with the access time I alluded to in my original post, but rather to keep the heads over the track whilst reading/writing is taking place. So you are comparing apples and oranges and declaring them equal.
just brew it! wrote:I have less patience for rude people. If this thread is an indication of how you're going to react every time anyone disagrees with you, perhaps this forum is not a good place for you.
Nec_V20 wrote:You jumped in assuming that JBI had his facts straight and proceeded to use that as the basis for criticising my original post
Chrispy_ wrote:If it seems like I have undue negativity towards you in this thread when treated as a single thread, it's because you attitude is simliarly abrasive and rude in several other threads I've seen you post in since you joined. I've just bitten my tongue in those instances. There is nothing to ever be gained from being rude, dismissive or personally attacking people. If you must do that, at least back up your argument with some hard evidence or an accurately quote what you think they said wrong. Accusing someone of saying something they didn't and then going off on a rant about it really is a pretty dumb way to behave, which is why I think there is now a lot of negativity towards you.
Nec_V20 wrote:Erm... wait a sec. So you intentionally cherry-picked results that show only a 3% difference (i.e. nowhere near statistically significant, given that you've just indicated that the results are varying all over the place), thereby undermining the very point you're trying to make?
hypothesis: screws make a difference
null hypothesis: screws make no difference
I picked the two results I thought would be fairest to compare (the lowest value of each run) given the limited amount of runs and did not want to accidentally overstate the difference in my original post.
Test runs without screws:
15.05
14.96
15.02
sigma = 0.0374
Test runs with screws
14.57
14.58
14.55
sigma = 0.005
Results from all test runs
15.05
14.96
15.02
14.57
14.58
14.55
sigma = 0.223
I don't see those results as "varying all over the place". There is a clear and persistent similarity of results within a test run as there are a complete and persistent difference between the runs. The standard deviation (sigma) within the runs is very narrow (0.037 and 0.005) i.e homogeneous whereas the standard deviation of the entire population of measurements is very wide (0.223) i.e. heterogeneous.
What are the chances of any values from a test run without screws overlapping (intersecting) a test run with screws? Even given the limited number of runs under each scenario I would still say that the chances of this are very slim indeed (about 0.1%) - well within the 5% confidence level needed for the differences between the two sets of measurements to be considered statistically significant.
Although I didn't like it (the lecturers were boring - like ketamine on legs boring) statistics was a part of my Psychology degree at Bonn University.