Why Not To Shout At Your Disk Array 125
Brendan Gregg of Sun's Fishworks lab has an interesting video demo up at YouTube demonstrating just how bad vibes, if expressed with sufficient volume in front of a rack full of disks, can cause a spike in disk latency. White noise, evidently, doesn't do them much harm. (Maybe they just feel awkward to get yelled at on camera.)
Youtube comments (Score:5, Funny)
he's like the crocodile hunter of loud server rooms
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...always made me laugh.
Yeah, they get you less tense.
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very nice.
I wish I had mod points.
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The video was pretty freaking hilarious as well!
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por que no?
Maybe this is why Windows gets slower all the time (Score:5, Funny)
People yelling too much at their computers
Re:Maybe this is why Windows gets slower all the t (Score:5, Funny)
hmm, bit of a chicken and the egg scenario there, isn't it?
is it slow because you yell at it, or do you yell at it because it is slow?
Either way, in the end it only degenerates into a downward spiral, where the computer gets slower and slower, while you get more and more pissed off at it and yell louder...
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Does it matter? Because they are on drugs anyway. You could switch off the screen, and they still would see the pretty oozing colors of...ehem... "Photoshop"...
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and I just remembered this kid [youtube.com] maybe if he was a little bit calmer the game would have loaded ;)
Why isn't this under idle? (Score:5, Informative)
It's been known for a long time vibrations are not good for discs (see notebooks). Even by early 90s music CDs had skip protection. If a disc skips, latency will of course momentarily increase. And with tolerances down even further, it's probably worse than back then.
In 10-15 years it won't matter anyway, almost everything will have SSD by then.
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On a bright side, you can read all the crap without having to tolerate that god aweful stylesheet!
Re:Why isn't this under idle? (Score:5, Interesting)
Prior to the advent of skip protection in portable CD players, you could make them skip for several seconds just by shouting at them briefly, because it took much longer to recover from the vibration than the duration of the shock itself.
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Yep. Even on my modern CD sound system with skip protection (cache), if I crank the volume up loud enough, the speakers will eventually vibrate the mechanism for so long as to cause the player to shudder and skip.
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Are you sure about this?
Let's say that I have my phone in my pocket, will that not affect?
Yes I agree that plain vanilla yelling will probably have no effect whatsoever. BUT what about radio waves?
Not to say it will stop me from buying SSD, just wondering out loud.
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SSD is digital. Radio is analog.
Your radio waves will need to cause at least 1.5v (or more, depending on the logic level of the device in question) to have a chance of flipping a line.
If the waves coming out of your phone can do that, call your doctor. You probably have at least 3 types of cancer.
Re:Why isn't this under idle? (Score:5, Funny)
There's BAD vibrations, and then there's GOOD Vibrations. [youtube.com]
Re:Why isn't this under idle? (Score:4, Interesting)
"Skip protection" on a hard drive is pointless. This is a fundamentally different scenario. With a CD, you can read the data *much* faster than you really need to read it, because you only need the data fast enough to convert it into sound. Plus you almost always know which piece of data needs to be read next, because the song is linear.
On the contrary, with a hard drive, read speed is (usually) the bottleneck, so you want the data sent to the processor as soon as you can pull it off the disk. Also, hard drives are much more random access, so you can't guess the location of the next read and read it before the CPU requests it. The only thing you can do is cache frequently accessed data in memory, which the operating system already does.
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Bullshit. Most files are read sequentially. Which is why most hard drive OS-level caches have read precaching.
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When you load one of my webpages, it usually reads about 300 different tiny files to process the request.
A drive like the one in TFA (if used for a webserver) is likely to be reading a few thousand different files every second, each one is on a different location on the disk and no way to determine which file will be read next.
SSD drives have shown to be multiple orders of magnitude faster than the most advanced hard drives available today for web servers.
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Try to run a webserver with caching built in. Chances are good 295 of those 300 files are going to be reloaded per page and can be stored in memory indefinitely. Last I heard, memory is still faster than SSD.
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Dear $DEITY don't start pulling that apart, I'm joking.
Interesting... (Score:5, Insightful)
Re:Interesting... (Score:5, Funny)
I would say yes. When I was a teen my mother walked into my room and started moaning about the mess.
Right then, windows blue screened and later I found the hard drive was completely dead. (Think it was a 15GB Maxtor or thereabouts) That cost me some pocket money to replace at the time.
If you have women living in the house, factor this into your backup procedure.
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You must still be in your Mum's basement. When I was a teen I had a 80MB Maxtor, and I left the basement 6 years ago! :-)
..to upgrade your 80mb (1000x80) drive? - Moore had you at firm ballgrip for quite some time, then.
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Even their own moms? Wow. I still live with my mamma. :P
Re:Interesting... (Score:5, Funny)
You made me wonder; if the the effect could be detected and "read", a you say, it would be possible to use it as a way of transmitting information to the computer by shouting at it.
I then remembered microphones.
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With a very loud set of speakers blaring at your drives, you'd do very well to step out of the room and close the door securely before shouting. Since most machine rooms i've been in were soundproof, i can't help but ask the question,
If you yell at your disk array but are not there to hear it, do you make a sound?
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This Discovery (Score:5, Funny)
How this guy actually made the discovery.
He must have let off quite a bit of steam towards that rack.
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Not to be a dry pedantic killjoy, but he was probably watching a young calf drinking.
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*sniff*
I'm dry and pedantic now
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Q: How did the <insert target cultural/racial/whatever group here> man die whilst drinking milk?
A: The cow sat on him.
Sorry, couldn't resist milking it for what it's worth
Screws in surgery (Score:1)
Years back I broke my ankle and had it screwed together for awhile. The screws are out now, but I've got them saved in a container and - other than the material - they really don't seem much different from those in my shop.
So was there some doctor who moonlighted as a carpenter, and one day looked at a broken, out-of-place bone... then at his workbench wood-projects ... then back at the bone.
Even today, looking at the X-ray of those screws firmly drilled through my bones gives me a bit of a creepy feeling,
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>white liquid that tasted so good
The first few brave adventurers were killed by bulls.
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'The very existence of flame-throwers proves that some time, somewhere, someone said to themselves, You know, I want to set those people over there on fire, but I'm just not close enough to get the job done.'
George Carlin
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'The very existence of flame-throwers proves that some time, somewhere, someone said to themselves, You know, I want to set those people over there on fire, but I'm just not close enough to get the job done.'
One of my favorite bits, to be sure, but one which becomes a lot less funny when you're being shot at by a couple [Germans|Japanese|*] with a machine gun through a tiny slit in a concrete bunker. That's about when being able to squirt a stream of flaming gasoline some arbitrary distance with some degree of accuracy begins to sound mighty useful...
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So you might say, there are people... and you want them on fire... but you just can't get close enough?
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The guy is a sysadmin. No surprises at all from this quarter as to how he came across such a discovery...
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JBODs? (Score:2)
...why?
I'm sure there's a good reason, but... He's using dtrace, right? Thus implying Solaris? Thus implying ZFS?
If you've got ZFS, why would you do JBOD?
Or did I just mis-hear him?
Re:JBODs? (Score:4, Informative)
A few reasons.
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ZFS RAID1 (and RAID-Z and RAID-Z2) can heal over corrupted blocks from the redundant copy. This is not possible with hardware RAID since it doesn't know which copy is valid.
Re:JBODs? (Score:5, Informative)
Re:JBODs? (Score:5, Interesting)
ZFS implements software RAID on top of JBOD. The box full of disks itself need not have any RAID controller, and if you're using RAID-Z, it would probably be a waste of money to spring for one, unless you go for the super-high-end for performance reasons.
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Or did I just mis-hear him?
"JBOD" in this context will be a reference to the style of disk array (eg: vs one with a RAID controller like the Dell MD3000), not the ZFS RAID level.
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Right. Question is whether the disk array is concatenating the drives somehow, or if ZFS can actually see each individual drive. I would think the latter would be much more useful.
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Right. Question is whether the disk array is concatenating the drives somehow, or if ZFS can actually see each individual drive. I would think the latter would be much more useful.
Given it's the ZFS folks at Sun, it will be the latter.
Is this a feature? (Score:2, Funny)
Might the the drives themselves be sensing the induced vibration via an embedded accelerometer and momentarily parking the heads to avoid damage? It seems like the marketing folks shouldn't have too hard of a time putting a positive spin on this behavior.
A rack full of disks (Score:2)
if expressed with sufficient volume in front of a rack full of disks
I wonder about the results of eliminating the superfluous "full of disks" part.
Interestingly enough, it's precisely here, where the omission would both be understood and not bring unwanted connotations.
Great.... (Score:4, Funny)
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You might like Accelerando by Michael Stross.
Sentient corporations and financial instruments and lawyer bots abound. It's a great book.
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Gah, thank you. I was typing that while half asleep.
Re:Sentient Corps and Lawyer Bots (Score:2)
In the wake of the Great Crash of 2008 that might take on scary new meaning.
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metal death machines
Just put these in a room with death metal machines. Problem solved.
White noise or not, it's the volume (Score:1)
Re:White noise or not, it's the volume (Score:5, Interesting)
I'm not an engineer or absolutely sure about how the brain works with white noise, but I had a job that I worked at that when I entered the freezer section, it didn't seem loud at all. Actually, it so much didn't seem loud that the few times I had to enter it, I forgot my ear plugs until I saw someone else using them.
Anyway, even though you couldn't really hear anything 'loud', if you tried to talk to anyway, you could barely hear them.
On to my question. If you have enough high amplitude random noise that is effectively destructive interference, would this make an enviorment where low amplitude sound could not be hear or even mechanically sensed easily?
I know using 'heard' may be incorrect in this context because perceived sound usually has no direct relation with what's mechanically going on with the sound waves.
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The effect you've described is called sound masking [wikipedia.org] (more generally, auditory masking [wikipedia.org]), so yes, but the cause isn't quite what you inferred (destructive interference).
Hard-drives as microphones?` (Score:2)
Nice, now I can use this to detect if people were loud in my server-room.
Do they also react to smell?
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Well, you can also use HDs as speakers:
http://www.afrotechmods.com/cheap/hdspeakers/hdspeakers.htm
I heard... (Score:1, Offtopic)
I heard that there is a place where they throw chairs at things...
Like with plants... (Score:1)
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Plants don't react to music, they react to the tiny shifts in air just above their stomata. The publication which reported this compared plants with music (read: vibrating air above the stomata) with plants in an enclosure without air vibrating (read:refreshing) above the stomata.
The experiment shows a difference, even if there's air-movement simply because air "sticks" to the surface of plant's leaves in close proximity - behaving like a fluid. Normal air ventila
It's the Enclosure (Score:2, Interesting)
Secret Fact : Ultrasonic noise at low volumes ! (Score:5, Interesting)
Secret Fact : Ultrasonic noise at low volumes is WORSE !
It took weeks to testing to get to the root issue of WD Raptors dropping in head seeks on very high end raid cards in tiny head movement seek benchmarks, but padding each JBOD drive in acoustic foam (shooting range foam), or testing one drive at a time, instead of 4 or 8, (either method works) increased I/O per second by 40% in a rack chassis.
40% more head movements per second if no ultrasonic noise entering drives !!!!!
This is VERY VERY RARE INFO, and only I, the head of Gigabyte in Asia, and two engineers in california know of this discovery.
And because I know no one on Slashdot will mod this up, and no one reads at 0 anymore, I can trust my astounding well researched secret shall remain secret.
Its sadly 100% factual.
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>And because I know no one on Slashdot will mod this up, and no one reads at 0 anymore, I can trust my astounding well researched secret shall remain secret.
For starters, make an account.
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Accounts are overrated. What happened to judging the content rather than the person?
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Never heard of such an alien philosophy. You must be new to the human race.
Re:Secret Fact : Ultrasonic noise at low volumes ! (Score:5, Informative)
You don't know too many greybeards do you? I'm surprised that modern drives are susceptible to ultrasonic under 80 khz but real old drives and drums were known to have problems with low audible frequency harmonics. A simple solution to this problem is stamp a butterfly like pattern in the arm of the head. The same thing works for power lines (which is what the small dumbbell looking things are near the insulators)
Re:Secret Fact : Ultrasonic noise at low volumes ! (Score:4, Informative)
Informative? Seriously? I hope this is some metamod effort at providing Karma... but just in case someone does take this seriously, I should take out a patent on this. That way, when Monster sells their butterfly-patterned head arms for 20K to audiophiles who don't like the lack of warmth in SSDs, I can get in on the racket.
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Sorry, there is prior art in the audio field too but feel free to send in cash to the patent office since they will rubber stamp it. I just want my cut or I can let them know about the prior art.
If you sing to them will the latency decrease? (Score:1)
I think that this discovery is just the beginning of a new and harmonious spiritual relationship between man and machine. Just imagine, DC engineers across the world singing beautiful harmonies to their storage arrays!!
Wonderful. ;-)
On colors of sound (Score:2)
White noise is just like white light: An even distribution of energy across the spectrum.
It makes perfect sense that white noise is less of a problem than an equal amount of noise at a specific frequency. Given a suitable frequency the material absorbing the energy will vibrate and even resonate. (That particular engineer's yelling, apparently, resonates well with the disks in the array of that video...)
It's the same reason why a bullet-proof west can make the impact of a bullet non-lethal: Spread out distr
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And are those kept near the nuclear wessels?
Sorry, could not resist.
Bad breath ... (Score:1)
"anti-vibration" damping?? (Score:1)
Warbirds? (Score:1, Interesting)
Also by Brendan Gregg (Score:5, Funny)
Also from Brendan Gregg comes the always useful /usr/bin/maybe [brendangregg.com]. Other funnies from him here [brendangregg.com].
before making fun of hard disks (Score:3, Funny)
the disk whisperer ... (Score:4, Funny)
I dub this guy the disk whisperer ...
Looking up? (Score:1)
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because all server admins are busy 24/7?
Server Admins are getting paid to 'watch' the servers. They have plenty of pseudo-free time. It's when stuff is breaking that they're busy. Not to mention a good admin in large server area will have software like that person had to watch drive latency.
What about my 300W Sub (Score:2)
That thing can shake my whole apartment. Is anyone testing what effect this thing has on my hard drives when listening to music/playing a game?
Now I'm terrified (Score:1)
Seems like I have a lot to worry about, I have a couple of disk arrays inside a 40-ft trailer that tends to rock in the wind...
The racks are shock-mounted, though.
You just scared them... (Score:1)
Nice Viral Marketing (Score:2)
I'm not being cynical in any way when I say I spent the last 1/2 hour checking out Fishworks due to the interesting analytics screen he used during the video. It occurred to me just now that's some (whether intentional or not) pretty effective viral marketing. LOL. The bad news is it appears Sun hasn't released Analytics as part of the base OpenSolaris distribution just yet. Too bad. I could just as easily use it to look at Veritas storage, assuming Veritas played nice with DTRACE. It'll be interesting
Disk Drives have a resonant frequency (Score:5, Interesting)
Disk drives have a resonant frequency
I've seen dramatic demonstrations of this over the years. One that stands out was a test of a Bryant drive sometime around 1970. In those days a 2 GB drive was at the edge of the envelope and Bryant was test-marketing just such a beast. It consisted of eight four-foot platters mounted four to a side on a shaft going through a monster of an electric motor. The heads were mounted on arms whose positioning was controlled by hydraulic cylinders big enough to be used as shocks on a pickup truck. The whole thing would not fit in the back of that pickup truck.
We were testing the thing with a program called the "Leese Bomb". Leese can identify himself or remain anonymous--I won't turn him in. The "Bomb" part was the nature of the test.
Basic tests in those days would involve writing a whole track and then reading it back and comparing what was read to what was written. You'd do this a number of times with different patterns to capture not only faults in the surface, but any sloppiness in the head control. The Leese bomb went one better.
It would write to the outside track, write to the inside track, read the outside track, read the inside track, and then compare. If the comparison failed it would repeat the test, and keep repeating untl it succeeded, counting the failures. If the test succeeded it would index the test both inward and outward so that the tracks tested would move toward the middle, cross, and continue. This test was superior in that it would capture dynamic flaws in the system as the distance the heads moved, and the time to move varied from max to zero.
In the case of the Bryant Drive (and, accidentally, an innocent Ramac drive at Caltech), the test found a resonant frequency. When the heads overshot their mark causing an error, the test stayed on the back and forth pattern, reinforcing the resonant motion with each cycle of the test. The drive started walking across the test floor in three-inch hops, but not for very long. In a few seconds, one of the shafts broke and one of the platters, a 500 pound disk rotating at 2400 rpm broke through the front of the unit and flew across the building until it was stopped, explosively, by one of the steel columns supporting the roof of the building. Miraculously, no one was hurt.
We gave up on Bryant for that application. Not long after that, CDC introduced its 200MB drives, and they passed the Leese Bomb with flying colours. Ten of them didn't take up any more room, or cost more, than the big Bryant, so our client was happy to go with that solution.
In any case the lesson is that, if it has moving parts, resonance is an issue.
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If I remember correctly, Nikola Tesla invented an apparatus to wreck buildings from within by finding building's resonant frequency and pounding at it.
Kinda like modern mass dampers, but active and, well, not damping much...
no longer requires the weirding module (Score:1)
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No, that is always recommended. How else are you going to get the bean counters to spring for some new kit?