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Vibration Killing Enterprise Disk Performance?
An anonymous reader writes "Is vibration killing disk performance? ZDnet reports on research that a carbon fiber anti-vibration rack increased random read performance by 56% to 246% and random write [performance] by 34% to 88%. Vibration is a known disk problem, but this is one of the few attempts to quantify its impact — which looks to be much greater than suspected."
So maybe sex in the server room IS a good idea! Not to mention all the puns you can make about racks.
Monstar L
Yes, already saw some crazed guy at Sun shout into an array of HDDs and it decreased performance.
http://www.youtube.com/watch?v=tDacjrSCeq4
Did anyone else think "how is Kirk going get out of this one"?
It's a lot easier to interfere with a moving head arm than it is to mess one up that's locked on a track, so this isn't surprising in the least for vibration to affect reads that require numerous long seeks. I'm surprised it's not worse than they've found.
Moving the head requires accelerated head stepping to top speed, stepping to close to the track, slowing down, stopping at the destination track, waiting for the head to settle, and reading an address block to find out where you managed to land. If you find you missed the track, you have to go through the whole seek process again. (usually only once more, those short adjustment hops are pretty reliable because they're lower speed) But that really hurts your single block read time.
Add to that the fact that the "high performance" drives are making more risky higher speed track changes, which increase the odds of missing your target and make the operation more sensitive to vibration. I've written direct HDD io code before, and sure, you can up the step speed to get very nice seek time boosts, but then you start missing your track and start getting reseeks. Usually you go with the fastest that's acceptably reliable, and that puts you on the bleeding edge of having problems, where things like vibration can run you off the deep end of the bell curve.
It wouldn't surprise me one bit if 50% of the "high performance drive" better speed is due to faster spindle speed, and the other half is faster (riskier) seek speed.
I work for the Department of Redundancy Department.
..at SustainIT 2010, Turner had a really good analysis. Still some gaps - figuring out what frequencies hurt the most, and how individual drive types respond to what, is necessary followon. How various vendors' drive units transfer vibration from the rack into the unit, into the drive carrier, into the drive. That sort of thing. Now that the phenomena is identified, a lot more to do on it.
At the least, keep performance sensitive drives away from large sources of environmental vibration, such as your AC unit and so forth.
the article does not say that it affects SSDs, but that it affects the SSD value proposition (aka, if you can spend little $$$ on carbon rack enclosures and get a significant seek performance increase, spending the large amount of $$$ to go full-ssd might not be as cost effective).
-- the cake is a lie
that CS disk drives are more sensitive to the vibration from physically coupled adjacent disk drives.
and
The problem is that most civilians don’t understand the problem and are not willing to pay to solve it.
Why should most people care about vibration caused by adjacent drives if most people only have one drive.
The other issue from TFA is that I can't believe a different rack can cause 250% performance improvement, unless you really stacked the deck against steel racks - loose screws, hard drives not properly mounted...? I assume this means that current server racks see I/O rates that are only 40% of what is advertised by manufacturers. Are we expected to believe that no one has noticed this? What about multiple drives in a server. There is no rack separating those drives. This reads like marketing, not real research.
http://www.greenplatformcorp.com/ is the site if you are interested and the "research" is several months old.
Is you comment based on this part of the article?
SSD value. Flash SSDs have fast random read access. But disks can improve their performance by 50% through vibration damping, that changes value proposition for SSDs.
I think the author is saying that if you can improve performance by 50% then there's less value in moving to SSDs that previously thought.
i guess the beach boys were wrong about those vibrations.
This is what you get when you drag a magnetic head across a surface. The sooner we get rid of mechanical storage the better. Solids are more robust, more energy efficient, quicker, denser, lighter. Cost and longevity issues are coming along. Yes, lets ditch the antiques already!
When our name is on the back of your car, we're behind you all the way!
So maybe sex in the server room IS a good idea! Not to mention all the puns you can make about racks.
Also, don't shout at your disks since it increases latency, as the guys at Sun Storage learned:
http://www.youtube.com/watch?v=tDacjrSCeq4
Plus a lube job and, definitely, Window cleaning.
This is news we needed 20 years ago. SSD is going to replace mechanical HD over the next couple of years making the whole vibration issue irrelevant.
Ah well better late than never I guess.
Weaselmancer
rediculous.
The disks all spin at roughly the same frequency (250Hz for a 15K RPM drive), so you could get some interesting resonance patterns in that frequency band as well as in its harmonics and frequencies that you get when you subtract rotational vibration spectrum of one drive from another. You can even hear these effects if you run two 7200 RPM drives in your desktop in a quiet room (assuming you don't have a dozen fans in the case that some people like to have for some reason).
The solutions is simple - dampen the drives to eliminate high frequency vibration transfer. Better yet, don't use screws to attach your drives at all. Use velcro.
It is going to matter only until price for SolidStateDisks becomes in line with what it should be
the article does not say that it affects SSDs, but that it affects the SSD value proposition (aka, if you can spend little $$$ on carbon rack enclosures and get a significant seek performance increase, spending the large amount of $$$ to go full-ssd might not be as cost effective).
My over one year old SSD drive can do ~6,000 under a database workload, the next-gen consumer SSD drives are reaching 60,000 random IOPS, and there are enterprise drives that can do over 150,000 IOPS with streaming speeds over a gigabyte per second.
This is a little like saying that Hayes has released a new 56K modem that resists line noise 50% better than existing modems, which affects the value proposition of 1Gbps fibre.
There's also no need to go "Full SSD". The newer virtualizing SAN arrays can migrate individual blocks of data between tiers of storage to place everything on the appropriate storage depending on the need for performance.
Paging Dr. Freud...
Sam ty sig.
..before I suspected something was not right and wrote a program continuously monitoring read speed. Then I started it, waited for the number to settle and put a disk into my CDROM. The reading speed decreased several times. After that I took the cdrom out, put it atop the case on a pile of foam rubber. That computer worked for 10 years more without any problems. The CDROM brand was Pioneer, if you care. HDDs were Maxtor and Western Digital. The story happen in 1997.
Note: I'm not a server guy, i'm not a LAMP guy, I'm not a OS guy nor a DBA. I deal with two objects in the datacenter, storage devices and switches that move packets (either FC or FICON) to storage devices.
First when I heard the term 'enterprise disks' I figured they were talking not about the drives themselves, but rather of the highend EMC, IBM, HDS variety (HP/SUN don't count b/c they rebrand HDS). There's no dampening in those arrays, they're basically racks/cabinets on wheels with casters on them to lock them down. If I was reading from a raw disk, then I could definitely see how vibration would have an impact, but with Enterprise disk arrays, there's so much cache (in the array, not on the drive) and read-ahead algorithms in place that I could see how users wouldn't notice the difference. I'm not so sure that EMC/HDS/IBM would be willing to build their disk arrays out of carbon fiber. Especially with the price conscious consumers like myself that love nothing more than my yearly meeting with my storage vendor to discuss $/GB.
I know of some companies that put their highend (Superdome/p690) servers on earthquake pads, which in the event of an earthquake the server can stay put while the floor shifts underneath.
I've actually experienced this problem first hand. I used to work at one of the above mentioned storage companies and we manufactured a disk shelf that had 8 drives in the front and 8 in the back. There was a metal divider in both the front and back that separated the box into quadrants. We noticed one year that there was a significant drive loss in the field and upon further investigation, we noticed that one slot in particular had an abnormally high failure rate. So we flew to one such site that had these suspect drive shelves, and measured the vibration of each disk in their disk shelves (they had about 100) using a tool that look pretty much like an accelerometer at the end of a pencil. Turns out that the drive location that had the highest number of failures, was not abnormally vibrating, but that a drive 4 spots away was. It seems that if a the drive next to the divider had a "high vibrational drive" it would set up a standing wave which would eventually cause another drive, which was perfectly fine from a manufacturing standpoint to fail.
Luckily, all my drives are mounted through silicone vibration isolators. Gotta love Antec case design! :D http://media.giantpachinkomachineofdoom.com/2007-02/blog/images/u1_array_supersize.jpg
Friend: "The NIC is misconfigured..." Me: "No prob, I'll just telnet in and fix it." *Silence*