Life and Death of Storage Devices 3: Mechanical Hard Disks

Mechanical hard drives have been inside computers for a very long time, perhaps since the late 1980s. Like floppy disks, they rely on magnetic technology to store data on discs but the technology had become so advanced and sensitive that they switched from plastic to metal and needed to put the discs in a very closed box.

The factories that make hard drives have no dust in them. The air processors remove it so that the magnetic particles in the dust doesn’t interfere with the magnetic particles in your drive. Before the hard drive leaves the factory they seal it making it impossible for dust to get inside but also impossible to repair.

Open Hard Disk platter

In all mechanical devices (as we saw with the failure of CD-ROM drives in part 1), there are parts that wear down from use or from a bad environment. For a hard drive the worst environment seems to be poor voltage control but temperature & handling also play roles. The motors in hard drives, especially laptop hard drives seem especially sensitive to input voltage fluctuations, or changes, from 230V.

In a hard drive there are motors which spin the discs, there are motors which move the read/write magnet arm and there are micro processors, chips which control the operations. If any of these are damaged, they are nearly impossible to fix. Umeme uchafu is probably the most common way for hard drives to die in Tanzania. A spike might kill the chips and  inconsistent voltage might wear down one or both of the very accurate motors.

If a laptop drive (2.5″) is dropped while it is running, the magnetic arm will crash into the discs causing a small dent or permanent destruction. If they’re dropped when turned off they’re impressively tolerant. Desktop sized (3.5″) hard drives are even more sensitive to being dropped, even when turned off.
Voltage Regulator, useful for laptops

Hard drive deaths are mysterious. Google has millions of hard drives in its facilities and it has published papers on the strange and random ways they fail. There are very few definite patterns, especially here in Africa. Even in a perfect environment with air conditioners, perfect power and care when handling they can fail. The most important things are to be preventative by using power cleaning devices and keeping backups.

One pattern which is worth noting is that once hard drives have lived past 1yr of consistent use they’re likely to continue to last, provided good voltage, handling.

In my opinion, you should get a voltage regulator to protect from inconsistent voltage on laptops and some form of AVS for a desktop. Keep in mind a voltage regulator will not protect from very big spikes or surges such as transformer explosions. At our TTC we have seen UPSs behind voltage regulators die even after the fuse has burnt.

Life and Death of Storage Devices 2: USB Flashes / Camera memory

As I’d mentioned in the first section of this series on CD-R and DVD-R, East Africa is a rough environment for storage devices. The last 3 years have seen an explosion of cheap flash devices into the computer world. This has come so far that in 2009 we can only sit and laugh at very unreliable 1MB floppies and even 100MB Zip disks that you might see at computer junk stores. Already in Tanzania 2GB flash drives are common and, at least abroad, quality 16GB flash drives are inexpensive (35000/= TSH).

Camera memory (like SD cards) and USB flash drives rely on much the same technology so I will discuss them together.

The moving parts of the mechanical hard drive cause ~90% (?) of their failures. The Flash drive has no moving parts inside. This might make you think that this means the USB Flash has no chance to break. You would be wrong though. If you are working in a windows environment with lots of viruses you’ve probably seen flash drives break more than once.

My understanding of Flash drive technology is not perfect (see Wikipedia & other references below) but it seems that there are several ways to design flash drives that make trade-offs for speed, capacity, or longevity (longer life). Ideally you want a good amount of all three. I suspect that many cheap manufacturers may use fewer, cheaper chips inside their drives to make capacity very large while hiding the shortened lifetime and speed. (A technical discussion of these are made in a part of this article on flash-based hard drives)

Longevity, or the length of the life of the flash drive is talking about the amount of times you can Write and Read anything from your drive. For quality flash drives, these numbers are generally very large: Millions or billions of times. There are even very advanced algorithms in the drives which balance out the load to reduce the damage. But on cheap flash drives or under the assault of many very kali Windows viruses for weeks after weeks you can quickly find that your flash is at the end of its days.

Viruses want to spread. The instructions that code a virus are not written carefully to help your computer, the programmer is very lazy. In East Africa most viruses specifically want to spread through your flash drive. This makes it very important for a virus to make sure that it gets onto a flash drive at any cost. The virus writer does not care whether he kills your flash in a month. He just wants to get his bad instructions onto your flash. This means that he will often just have his program write Over and Over and Over again to your flash drive blinking its light all day long. When you’re doing a hundred reads and writes a minute, soon your millions and billions of operations are exhausted and gone.

If you notice your flash drive acting strange or slow you might only have a few more chances to rescue your data. Though you should always keep backups of your flash somewhere, in this situation make a special backup as soon as possible! You usually have a few more Read operations than Write operations with your drive and that could save your data. In the fourth tip of this series I will go into detail on the programs testdisk and photorec and which can be used to rescue files on a drive that Windows/Linux/Solaris will not read.

There are also major issues with fake drives. Beware! My counterparts here at Mpwapwa have seen several weak flash drives labeled “Sony Vaio” which will report to Windows (or Linux, Solaris) that they are, say, 32gb. When you put files onto them the files appear to transfer. This is fake though, the real size of the drive is 512MB. When you take files that are bigger than 512mb off of the flash again it will say that your file is corrupt. We have also seen that these flash drives fail much quicker than other flash drives.

Life and Death of Storage Devices 1: CD-R/DVD-R Discs

In Tanzania we are using 3 different kinds of hardware to store and share our data: CD-Rs/DVD-Rs discs, Flash drives, and (mechanical) hard disks. TZ is a harsh environment for each of these kinds of storage. I am sure you have seen each of them fail. The interesting thing is that each of them stop working in a different way. In this post I will describe the failure mode of each kind of device, as I understand them.

Dye on old CD-R is starting to dissolve, Via Wikipedia

CD-R/DVD-R:

CD-R and DVD-R are based on a similar idea. There is a layer of the disc which is reflective like a mirror. There is at least one other layer which has some special ink frozen in plastic and one more extra layer of plastic to try to protect the ink. The red laser inside the DVD or CD reader tries to change the ink or dye in millions of places/dots so that it can store data.

The most common way CD/DVD fail is by becoming scratched. As those of us that piga deki every couple days know, Africa is quite a dusty place–that dust scrapes at the plastic very easily leaving places where the laser is trying to read. Another possible way to damage a dvd is by breaking it so the ink spills a little or the reflective layer doesn’t reflect the laser back to the DVD player eye.

Perhaps the most interesting failure of CD/DVD is when a certain bacteria eats away at the reflective layer. Also if you buy certain  DVD-R/CD-R the ink formula may be low quality and might not hold the dots “color” very well. As the “color” changes around the disc the data is slowly lost. If you leave a CD-R in the sun you might also notice data loss. There are more details on the Wikipedia page for CD-R.

For a larger hardware problem, with the dirt in the air, the mechanics of the CD-ROM drive often seem to fail so that the door to the drive does not open reliably. I have read some accounts that it is because the rubber band/string is getting stretched and so the drive doesn’t recognise that the eject button is pressed as easily. According to websites, you can replace the band and it will often start to eject properly again but we haven’t tried it at our college.

Umeme Uchafu and You.

Dirty electricity is a big problem in Tanzania. Viruses may cause most of Tanzania’s software problems but dirty electricity is accountable for most of the hardware issues that we find here. Unlike software, there is often no way to recover from a hardware failure without spending more money. That means even though in my mind a virus scanner is lazima–an unquestionable must, correct power protection is even more important.

The problem with power protection is that there is no wisdom on the issue from Western developed countries (unlike with viruses). There are power protection items available here in Tanzania that we can use to protect against the bad power here but they are often not widely understood. In the US and Europe there are not so many worries about power, besides perhaps lightening strikes.

I think the most important rule is to keep at least one piece of equipment between you and Tanesco. I recommend some of the devices below. Here are some options I researched last weekend at a certain direct dealer in downtown Morogoro (between dala stand & soko):

Solatek AVS 30A

Prices are listed in TSH

• Voltage Regulation: Blue Samlex (not fake) Voltage Regulators, clean wild voltage to lengthen the life of laptop hard drives. Will not protect transformer explosions, etc.
  • 500W (4 laptops or 1 desktop): 38500
  • 1000W (2 desktops): 48500
  • 1500W (3-4 desktops):62500
• Voltage surge protectors strips (protect from lightening or perhaps transformer explosion)
  • Solatek Multiguard Surge+Spike (5 plug, 13A): 39500
  • Tripplite: 24000 (?)
• Solatek AVS – Automatically cut the power if power is poor, return it after short timer. Free warranty service is available at AAPower on Zanake street in Dar es Salaam. I plan to visit this week.
  • COMMGuard (1 desktop, laptop): 28500
  • AVS 13A (3-4 desktops?): 70000
  • AVS 15A (round holes, 5 desktops?):  78500
  • AVS 30A (7-10 desktops?): 92500

I have not yet had a chance to price UPSs. Still, I would like to post the reminder that Laser printers & copiers should be protected separately from other devices as they suddenly draw huge amounts of currents when the toner lases (see wikipedia). If one is plugged into a UPS with a computer in the wrong port you will, in a short time, kill the UPS, computer and printer.

Kurudi tena

So the past 19 days since the only post this month have been very busy so I’ve been neglecting the blog. I hope to come back significantly this coming week. I have a new series on how different kinds of storage media devices fail in East Africa and a few prices on power coming up. The virus series is on my plate too.

Two weeks ago we installed the latest Solaris “image” at our college and installed several software updates after it. I’ve recorded my instructions and have shared it with the project so that the next version of the Solaris image can include only the freshest software like Adobe Acrobat reader, Firefox, and Open Office. In computer administration, an “image” is a very complete collection of all the configuration that is done to a computer. It is then arranged into a DVD or file so that it can be shared easily with other people (or colleges). When you install it, everything is already set up for you, just as the team at Morogoro left it. Later, I hope to cover imaging for Windows computers with Clonezilla to make your life easier.

Last week Peace Corps TZ officially added Windows virus and power protection to the skills that new volunteers are required to study and learn during their three month training, after Swahili. I think this underlines the situation here. I feel that viruses are getting more frustrating, even fewer of them are being detected by antivirus and there are many more of them. It also focuses us on power protection: please listen to my message in my umeme uchafu articles: spending a small amount now on prevention will save your departments a lot of money later.

I also held a small seminar here with a special guest from Mzumbe Mbeya to explain the benefits of Ubuntu Linux–it is always virus free (from flash drives) and has nearly all of the programs & features of Windows that Solaris is missing. Keep in mind that leaving Windows is an easier option than it sounds like when you get frustrated cleaning peoples’ USB flashes and slow computers. Just download, burn and install the CD. It installs much faster and easier than Windows. You can even order a free one to be sent to Tanzania! (linkage)

Virusi si jambo gumu: How Viruses Trick You Part 1 of 3

A flash drive in Tanzania may seem complicated with all of the viruses that can get onto them and cause every kind of problem. The problems with them that Tz computer users see every day all have pretty basic explanations, especially when they are still on the flash drive. In the next three virus tips I will explain:

1. the idea of a virus (this tip),
2. the way that most common USB Flash virus spread on to Windows XP
3. and their common hiding places.

Virus: Work is Work; Don't hate my work, it doesn't help me. Us: Take your panga somewhere else

In one sense, computer viruses are like biological viruses. Viruses have two goals:

1. To spread their instructions to other computer, and
2. To do something else

Any one virus does not want to completely break your computer with these goals. If it breaks your computer then it can’t spread from your computer to new computers and it is a weak virus. The “do sometime else” includes making our computers run slowly, do strange things, and sometimes stop working altogether. Usually after many viruses have arrived, they start interfering with each-other to make your computer very slow or crash.

Though viruses seem almost as dangerous and flexible as their biological viruses, they are written by people to spread a message, steal information, use your computer’s speed, or generally hurt Microsoft. As far as we know, no one writes viruses to deprive African school children of the opportunity to use computers but in our world, this is most often the effect.

We need to think about how viruses spread to help protect our computers from the first virus.

• In Tanzania, the common way to spread a virus is through a USB flash drive when the user runs a virus program on it by double clicking on the main drive or fake items.
• A few years ago in the rest of the world, email was the most common way to spread viruses. Here in TZ though, if you have a Yahoo email account, it already scans all your messages.
• An important and often forgotten way viruses can come is when you download new software ovyoovyo without knowing that the person or website it is coming from is trustworthy. You should be very careful when you install internet software when it isn’t from a big company like Microsoft or Yahoo. The bad software is a like fake Chinese TVs or pasi–it looks almost right on the outside but inside it doesn’t work and might start a fire.

A virus usually cannot enter the computer through music or video. It needs to be free to give specific bad instructions to the central processing unit (CPU). Running programs talk to the CPU directly but playing music & video does not. This means that viruses can pretend to be music but that real music rarely has a virus inside. Also, clicking on a real folder cannot start a virus but clicking on a program with a picture (icon) that looks like a folder can be very bad. Viruses are computer tricks-Vinakudanganya kuwezesha kazi yake. The worst trick is one most Tz users don’t even see. They click fake movies and fake folders and dirty drives without seeing the virus.

Hata usipokuwa na virus scanner, If your Windows XP computer is updated to Service Pack 2 or 3 and you are careful , then there is no reason you should get any viruses. Your computer is not giving you viruses, you are being tricked to double click and run the virus program. If people on your computer never double click or right click your USB flash drive in My Computer, then you will never get viruses. Instead, you should find, click on the Folders button at the top and then left click once on your flash drive on the left side of the window as pictured.

Screen shot showing the dangerous place to double click in My Computer. If you have an completely updated virus scanner you can worry less about this, otherwise be careful.

Why? Read the next tip on Autorun & Autoplay in Windows XP in this series on Viruses coming soon!

Some portions of this posting were written in collaboration with Aron, an A-Level teacher at Bihawana Secondary School.