Noise from Shaving

About 10 years ago I started using an electric shaver. An electric shaver is more convenient to use as it doesn’t require any soap, foam, or water. It is also almost impossible to cut yourself properly with an electric shaver which is a major benefit for anyone who’s not particularly alert in the morning. Generally my experience of electric shavers has been good, although the noise is quite annoying.

Recently a friend told me that an electric shaver is as noisy as a chain-saw. Given the inverse-square law and the fact that the shaver operates within 1cm of my ears that sounds plausible. So the risk of hearing loss is a great concern. Disposable ear plugs are very cheap and they can be used multiple times (they don’t get particularly dirty while shaving or get squashed in the short time needed to shave). So for a few weeks I’ve been using ear plugs while shaving which reduces the noise and presumable saves me from some hearing damage – although after 10 years of using electric shavers I may have already sustained some damage.

According to Cooper Safety their ear plugs reduce noise by 29dB, [1] I presume that the cheap ones I bought from Bunnings would be good for at least 15dB.

According to Better Hearing Sydney the noise from an electric shaver is typically around 90dB, less than the 100dB that is typical of a chain-saw [2]. So if my ear-plugs are good for 15dB then they would reduce the noise from a typical electric shaver to 75dB which is well below the 85dB that will cause hearing damage. Given that the noise from a typical shaver is only slightly above the damage threshold it seems that I might not need particularly good ear-plugs when shaving.

A quick scan of shaver reviews indicates that the amount of noise differs by brand and technology. The Hubpages review suggests that rotary shavers tend to make less noise than foil shavers [3], but I’m sure that it varies enough between brands that some rotary shavers are louder than the quietest foil shavers. It seems that the best thing to do when buying a new shaver would be to go to a specialised shaver shop (which has many models on offer) and get the staff to demonstrate them to determine which is the quietest. If a typical shaver produces 90dB then it seems likely that one of the more quiet models would produce less than 85dB.

Another item on my todo list is to buy a noise meter to measure the amount of noise produced in the places where I spend time. There are some Android apps to measure noise, I’m currently playing with the Smart Tools Co Sound Meter [4] which gives some interesting information. The documentation notes that phone microphones are limited to the typical volume and frequencies of human voice, so my Galaxy S3 can’t measure anything about 81dB. My wife’s Nexus 4 doesn’t seem to register anything above 74dB. Additionally there is some uncertainty about the accuracy of the microphone, there is a calibration feature but that requires another meter. Anyway the Sound Meter app suggests that my shaver (a Philips HQ7380/B) produces only 71dB at the closest possible range – and drops down to 67dB at the range I would use if I grew sideburns.

Conclusion

Getting a proper noise meter to protect one’s hearing seems like a good idea. An Android app for measuring noise is a good thing to have, even though it’s not going to be accurate it’s convenient and will give an indication.

When buying a shaver one should listen to all the options and choose a quiet one (I might have got a quiet one by luck).

Sideburns seem like a good idea if you value your hearing.

• [1] http://www.coopersafety.com/NoiseReduction.aspx
• [2] http://www.betterhearingsydney.org.au/content/view/46/53/
• [3] http://tinyurl.com/ojxfx9t
• [4] https://play.google.com/store/apps/details?id=kr.sira.sound

Syndicated 2013-05-23 09:56:22 from etbe - Russell Coker

No Backups WTF

Some years ago I was working on a project that involved a database cluster of two Sun E6500 servers that were fairly well loaded. I believe that the overall price was several million pounds. It’s the type of expensive system where it would make sense to spend adequately to do things properly in all ways.

The first interesting thing was the data center where it was running. The front door had a uniformed security guard and a sign threatening immediate dismissal for anyone who left the security door open. The back door was wide open for the benefit of the electricians who were working there. Presumably anyone who had wanted to steal some servers could have gone to the back door and asked the electricians for assistance in removing them.

The system was poorly tested. My colleagues thought that with big important servers you shouldn’t risk damage by rebooting them. My opinion has always been that rebooting a cluster should be part of standard testing and that it’s especially important with clusters which have more interesting boot sequences. But I lost the vote and there was no testing of rebooting.

Along the way there were a number of WTFs in that project. One of which was when the web developers decided to force all users to install the latest beta release of Internet Explorer, a decision that was only revoked when the IE install process broke MS-Office on the PC of a senior manager. Another was putting systems with a default Solaris installation live on the Internet with all default services running, there’s never a reason for a database server to be directly accessible over the Internet.

No Backups At All

But I think that the most significant failing was the decision not to make any backups. This wasn’t merely forgetting to make backups, when I raised the issue I received a negative reaction from almost everyone. As an aside I find it particularly annoying when someone implies that I want backups because I am likely to stuff things up.

There are many ways of proving that there’s a general lack of competence in the computer industry. But I think that one of the best is the number of projects where the person who wants backups has their competence questioned instead of all the people who don’t want backups.

A decision to make no backups relies on one of two conditions, either the service has to be entirely unimportant or you need to have no bugs in the OS or hardware defects that can corrupt data, no application bugs, and a team of sysadmins who never make mistakes. The former condition raises the question of why the service is being run and the latter is impossible.

As I’m more persistent than most people I kept raising the issue via email and adding more people to the CC list until I got a positive reaction. Eventually I CC’d someone who responded with “What the fuck” which I consider to be a reasonable response to a huge and expensive project with no backups. However the managers on the CC list regarded the use of profanity in email to be a much more serious problem. To the best of my knowledge there were never any backups of that system but the policy on email was strongly enforced.

This is only a partial list of WTF incidents that assisted in my decision to leave the UK and migrate to the Netherlands.

Not Doing Much

About a year after leaving I returned to London for a holiday and had dinner with a former colleague. When I asked what he was working on he said “Not much“. It turned out that proximity to the nearest manager determined the amount of work that was assigned. As his desk was a long way from the nearest manager he had spent about 6 months getting paid to read Usenet. That wasn’t really a surprise given my observations of the company in question.

Syndicated 2013-05-21 09:43:37 from etbe - Russell Coker

Advice on Buying a PC

A common topic of discussion on computer users’ group mailing lists is advice on buying a PC. I think that most of the offered advice isn’t particularly useful with an excessive focus on building or upgrading PCs and on getting the latest and greatest. So I’ll blog about it instead of getting involved in more mailing-list debates.

A Historical Perspective – the PC as an Investment

In the late 80′s a reasonably high-end white-box PC cost a bit over $5,000 in Australia (or about $4,000 without a monitor). That was cheaper than name-brand PCs which cost upwards of $7,000 but was still a lot of money. $5,000 in 1988 would be comparable to $10,000 in today’s money. That made a PC a rather expensive item which needed to be preserved. There weren’t a lot of people who could just discard such an investment so a lot of thought was given to upgrading a PC.

Now a quite powerful desktop PC can be purchased for a bit under $400 (maybe $550 if you include a good monitor) and a nice laptop is about the same price as a desktop PC and monitor. Laptops are almost impossible to upgrade apart from adding more RAM or storage but hardly anyone cares because they are so cheap. Desktop PCs can be upgraded in some ways but most people don’t bother apart from RAM, storage, and sometimes a new video card.

If you have the skill required to successfully replace a CPU or motherboard then your time is probably worth enough that getting more value out of a PC that was worth $400 when new and is worth maybe $100 when it’s a couple of years old probably isn’t a good investment.

Times have changed and PCs just aren’t worth enough to be bothered upgrading. A PC is a disposable item not an investment.

Buying Something Expensive?

There are a range of things that you can buy. You can spend $200 on a second-hand PC that’s a couple of years old, $400 on a new PC that’s OK but not really fast, or you can spend $1000 or more on a very high end PC. The $1000 PC will probably perform poorly when compared to a PC that sells for $400 next year. The $400 PC will probably perform poorly when compared to the second-hand systems that are available next year.

If you spend more money to get a faster PC then you are only getting a faster PC for a year until newer cheaper systems enter the market.

As newer and better hardware is continually being released at low enough prices that make upgrades a bad deal I recommend just not buying expensive systems. For my own use I find that e-waste is a good source of hardware. If I couldn’t do that then I’d buy from an auction site that specialises in corporate sales, they have some nice name-brand systems in good condition at low prices.

One thing to note is that this is more difficult for Windows users due to “anti-piracy” features. With recent versions of Windows you can’t just put an old hard drive in a new PC and have it work. So the case for buying faster hardware is stronger for Windows than for Linux.

That said, $1,000 isn’t a lot of money. So spending more money for a high-end system isn’t necessarily a big deal. But we should keep in mind that it’s just a matter of getting a certain level of performance a year before it is available in cheaper systems. Getting a $1,000 high-end system instead of a $400 cheap system means getting that level of performance maybe a year earlier and therefore at a price premium of maybe $2 per day. I’m sure that most people spend more than $2 per day on more frivolous things than a faster PC.

Understanding How a Computer Works

As so many things are run by computers I believe that everyone should have some basic knowledge about how computers work. But a basic knowledge of computer architecture isn’t required when selecting parts to assemble to make a system, one can know all about selecting a CPU and motherboard to match without understanding what a CPU does (apart from a vague idea that it’s something to do with calculations). Also one can have a good knowledge of how computers work without knowing anything about the part numbers that could be assembled to make a working system.

If someone wants to learn about the various parts on sale then sites such as Tom’s Hardware [1] provide a lot of good information that allows people to learn without the risk of damaging expensive parts. In fact the people who work for Tom’s Hardware frequently test parts to destruction for the education and entertainment of readers.

But anyone who wants to understand computers would be better off spending their time using any old PC to read Wikipedia pages on the topic instead of spending their time and money assembling one PC. To learn about the basics of computer operation the Wikipedia page for “CPU” is a good place to start. Then the Wikipedia page for “hard drive” is a good start for learning about storage and the Wikipedia page for Graphics Processing Unit to learn about graphics processing. Anyone who reads those three pages as well as a selection of pages that they link to will learn a lot more than they could ever learn by assembling a PC. Of course there’s lots of other things to learn about computers but Wikipedia has pages for every topic you can imagine.

I think that the argument that people should assemble PCs to understand how they work was not well supported in 1990 and ceased to be accurate once Wikipedia became popular and well populated.

Getting a Quality System

There are a lot of arguments about quality and reliability, most without any supporting data. I believe that a system designed and manufactured by a company such as HP, Lenovo, NEC, Dell, etc is likely to be more reliable than a collection of parts uniquely assembled by a home user – but I admit to a lack of data to support this belief.

One thing that is clear however is the fact that ECC RAM can make a significant difference to system reliability as many types of error (including power problems) show up as corrupted memory. The cheapest Dell PowerEdge server (which has ECC RAM) is advertised at $699 so it’s not a feature that’s out of reach of regular users.

I think that anyone who makes claims about PC reliability and fails to mention the benefits of ECC RAM (as used in Dell PowerEdge tower systems, Dell Precision workstations, and HP XW workstations among others) hasn’t properly considered their advice.

Also when discussing overall reliability the use of RAID storage and a good backup scheme should be considered. Good backups can do more to save your data than anything else.

Conclusion

I think it’s best to use a system with ECC RAM as a file server. Make good backups. Use ZFS (in future BTRFS) for file storage so that data doesn’t get corrupted on disk. Use reasonably cheap systems as workstations and replace them when they become too old.

Update: I find it rather ironic when a discussion about advice on buying a PC gets significant input from people who are well paid for computer work. It doesn’t take long for such a discussion to take enough time that the people involved could spent their time working instead, put enough money in a hat to buy a new PC for the user in question, and still had money left over.

• [1] http://www.tomshardware.com/

Syndicated 2013-05-21 04:58:03 from etbe - Russell Coker

Advice on Buying a PC

A common topic of discussion on computer users’ group mailing lists is advice on buying a PC. I think that most of the offered advice isn’t particularly useful with an excessive focus on building or upgrading PCs and on getting the latest and greatest. So I’ll blog about it instead of getting involved in more mailing-list debates.

A Historical Perspective – the PC as an Investment

In the late 80′s a reasonably high-end white-box PC cost a bit over $5,000 in Australia (or about $4,000 without a monitor). That was cheaper than name-brand PCs which cost upwards of $7,000 but was still a lot of money. $5,000 in 1988 would be comparable to $10,000 in today’s money. That made a PC a rather expensive item which needed to be preserved. There weren’t a lot of people who could just discard such an investment so a lot of thought was given to upgrading a PC.

Now a quite powerful desktop PC can be purchased for a bit under $400 (maybe $550 if you include a good monitor) and a nice laptop is about the same price as a desktop PC and monitor. Laptops are almost impossible to upgrade apart from adding more RAM or storage but hardly anyone cares because they are so cheap. Desktop PCs can be upgraded in some ways but most people don’t bother apart from RAM, storage, and sometimes a new video card.

If you have the skill required to successfully replace a CPU or motherboard then your time is probably worth enough that getting more value out of a PC that was worth $400 when new and is worth maybe $100 when it’s a couple of years old probably isn’t a good investment.

Times have changed and PCs just aren’t worth enough to be bothered upgrading. A PC is a disposable item not an investment.

Buying Something Expensive?

There are a range of things that you can buy. You can spend $200 on a second-hand PC that’s a couple of years old, $400 on a new PC that’s OK but not really fast, or you can spend $1000 or more on a very high end PC. The $1000 PC will probably perform poorly when compared to a PC that sells for $400 next year. The $400 PC will probably perform poorly when compared to the second-hand systems that are available next year.

If you spend more money to get a faster PC then you are only getting a faster PC for a year until newer cheaper systems enter the market.

As newer and better hardware is continually being released at low enough prices that make upgrades a bad deal I recommend just not buying expensive systems. For my own use I find that e-waste is a good source of hardware. If I couldn’t do that then I’d buy from an auction site that specialises in corporate sales, they have some nice name-brand systems in good condition at low prices.

One thing to note is that this is more difficult for Windows users due to “anti-piracy” features. With recent versions of Windows you can’t just put an old hard drive in a new PC and have it work. So the case for buying faster hardware is stronger for Windows than for Linux.

That said, $1,000 isn’t a lot of money. So spending more money for a high-end system isn’t necessarily a big deal. But we should keep in mind that it’s just a matter of getting a certain level of performance a year before it is available in cheaper systems. Getting a $1,000 high-end system instead of a $400 cheap system means getting that level of performance maybe a year earlier and therefore at a price premium of maybe $2 per day. I’m sure that most people spend more than $2 per day on more frivolous things than a faster PC.

Understanding How a Computer Works

As so many things are run by computers I believe that everyone should have some basic knowledge about how computers work. But a basic knowledge of computer architecture isn’t required when selecting parts to assemble to make a system, one can know all about selecting a CPU and motherboard to match without understanding what a CPU does (apart from a vague idea that it’s something to do with calculations). Also one can have a good knowledge of how computers work without knowing anything about the part numbers that could be assembled to make a working system.

If someone wants to learn about the various parts on sale then sites such as Tom’s Hardware [1] provide a lot of good information that allows people to learn without the risk of damaging expensive parts. In fact the people who work for Tom’s Hardware frequently test parts to destruction for the education and entertainment of readers.

But anyone who wants to understand computers would be better off spending their time using any old PC to read Wikipedia pages on the topic instead of spending their time and money assembling one PC. To learn about the basics of computer operation the Wikipedia page for “CPU” is a good place to start. Then the Wikipedia page for “hard drive” is a good start for learning about storage and the Wikipedia page for Graphics Processing Unit to learn about graphics processing. Anyone who reads those three pages as well as a selection of pages that they link to will learn a lot more than they could ever learn by assembling a PC. Of course there’s lots of other things to learn about computers but Wikipedia has pages for every topic you can imagine.

I think that the argument that people should assemble PCs to understand how they work was not well supported in 1990 and ceased to be accurate once Wikipedia became popular and well populated.

Getting a Quality System

There are a lot of arguments about quality and reliability, most without any supporting data. I believe that a system designed and manufactured by a company such as HP, Lenovo, NEC, Dell, etc is likely to be more reliable than a collection of parts uniquely assembled by a home user – but I admit to a lack of data to support this belief.

One thing that is clear however is the fact that ECC RAM can make a significant difference to system reliability as many types of error (including power problems) show up as corrupted memory. The cheapest Dell PowerEdge server (which has ECC RAM) is advertised at $699 so it’s not a feature that’s out of reach of regular users.

I think that anyone who makes claims about PC reliability and fails to mention the benefits of ECC RAM (as used in Dell PowerEdge tower systems, Dell Precision workstations, and HP XW workstations among others) hasn’t properly considered their advice.

Also when discussing overall reliability the use of RAID storage and a good backup scheme should be considered. Good backups can do more to save your data than anything else.

Conclusion

I think it’s best to use a system with ECC RAM as a file server. Make good backups. Use ZFS (in future BTRFS) for file storage so that data doesn’t get corrupted on disk. Use reasonably cheap systems as workstations and replace them when they become too old.

• [1] http://www.tomshardware.com/

Syndicated 2013-05-21 04:57:03 from etbe - Russell Coker

Voltage Inside a Car

I previously wrote a post with some calculations about the power supplied to laptops from a car battery [1]. A comment on the post suggested that I might have made a mistake in testing the Voltage because leaving the door open (and thus the internal lights on) will cause a Voltage drop.

So I’ve done some more tests:

In my previous tests I recorded 12.85V inside my car (from the front power socket which although having the same connector as a cigarette lighter isn’t designed for lighting cigarettes) and 13.02V from the battery terminals – a 0.17V difference. In my tests today I was unable to reproduce that but I think that my biggest mistake was to take the reading too quickly. Today I noticed that it took up to a minute for the Voltage to stabilise after opening a door (the Voltage dips after any current draw and takes time to recover) so a quick reading isn’t going to be accurate.

My car is a Kia Carnival which has two sockets in the front for power and for actually lighting cigarettes. The one for lighting cigarettes has a slightly lower Voltage and only works when the ignition is turned on. The car also has a power socket in the boot (the trunk for US readers) which delivers the same Voltage as the power socket in the front.

Also one thing to note is that today is a reasonably cold day (16.5C outside right now) and my car hasn’t been driven since last night so the battery would be quite cold (maybe 12C or less). My previous measurements were taken in summer so the battery would have been a lot warmer and therefore working more effectively.

Conclusion

The Voltage drop from turning on the internal lights surprised me, I had expected that a car battery which is designed to supply high current wouldn’t be affected by such things. Certainly not to give a 2% Voltage drop! The Voltage difference from reading inside the car and at the battery terminals might be partly due to the apparent lead coating on the terminals, I pushed the probes of my multimeter beneath the surface of the metal and got a really good connection.

The 14% Voltage increase when the engine was running was also a surprise. It seems to me that if you are running a power hungry device (such as a laptop) it would be a good idea to disconnect it when the engine is turned off. A 14% higher voltage will give a 14% lower current if the PSU is efficient and therefore less problems with heat in the wiring and less risk of blowing a fuse.

Also it’s a good idea to be more methodical about performing tests than I was before my last post. There are lots of other tests I could run (such as testing after the engine has been running for a while) but at the moment I don’t have enough interest in this topic to do more tests. Please leave a comment if there’s something interesting that you think I missed.

• [1] http://etbe.coker.com.au/2013/01/24/power-supplies-wires/

Syndicated 2013-05-17 02:57:47 from etbe - Russell Coker