Disk Mirroring

[Tannin]

Originally Posted by Leif

It's worth pointing out that hard disk crashes are not that rare.

This depends on three main factors:

1: The way the drives are handled, both in the wharehouse/distribution channel and by the installation technician. Hard drives are very sensitive to shock, and although a nasty bump very rarely shows up with an immediate failure, it greatly increases the risk of failure later on. Many people don't fully realise this and pay only lip service to what is, in reality, the #1 rule of hard drive safety - treat them like they were made out of eggshells! This is why we only ever buy drives from a known and trusted distributor with a track record of doing it right, and even then always buy more than 10 units at once. (Hard drives come ex factory in boxes of 20. If you order 5 drives or 9, the warehouse guy takes them out of the box, maybe packs them properly, maybe doesn't, maybe bangs them down on his desk, maybe doesn't, then ships them to you. If you buy (e.g.) 15 drives, human nature being what it is, the warehouse guy takes the other five drives out of the box and your 15 stay nice and safe in the factory carton, which is proof against even couriers and truck drivers. Best, of course, is to simply buy a box of 20.) Obviously, you don't want 20 hard drives - but you can buy your drive from someone who does buy them that way, and who knows how important it is to look after them.

2: The quality of the drives used. There are major differences in reliability between different brands of drive. Seagate/Maxtor and Western Digital drives have a failure rate measured in units per hundred, typically a modest single-digit number per hundred, but higher for a bad model. Samsung drives have a failure rate measured in units per thousand, and it's a small single digit. I don't see enough Hitachi drives to put a number on their RMA rate, but it's probably closer to the Samsung figure than the Seagate/WD one. (Just guessing on this last.)

3: Clint's Rule. ("Do I feel lucky?")

[robski]

The most common reason for disk failure is when the heads get mucked up by oil when PC is powered off. Especially if the drives run for very long periods ( months ) between power down cycles. The oil from the spindle bearings can leak and spray over the disk surface which is not a big problem in itself on the active area of the disk. However when you power down the heads are parked on a non active area of the disk which by now have a thicker film of oil.

[robski]

I agree with Tannin some drive manufacturers are orders on magnitude better than others. I've seen IBM drives die after a short period. I was testing some software where the system was writing about 100 files a second for 2 to 3 days. The IBM drive died and refused to pass the post test. Sun Microsystems replaced with a Seagate so far it's held up.

[nirofo]

I wouldn't dare rely on keeping all my thousands of scanned images, totalling hundreds of gigabytes, on a hard drive of any description. In the course of a year I repair and maintain many computer systems, some with large hard drives, some with raid arrays, the majority of these come in with some kind of hard disk fault! Sometimes it is quite easy to save the files stored on these disks to a CD or a DVD, slap in a new drive, re-boot the system and everything's fine. Then there are the drives that are completely trashed for one reason or another, normal file restoration and saving with these drives if not impossible can be extremely expensive, usually entailing a trip to a specialist data recovery company. In either case the average computer user doesn't want the hassle and certainly doesn't want the cost! I backup my scans and digital images on a regular basis, I scan and process 10 then save to DVD-R using Nero Burning Rom or Nero Express. Working this way the most files I can lose will be 10, it only takes a few minutes to burn 10 images to DVD, it can take hours to scan and process in Photoshop 10 images to the computer.

nirofo.

[Leif]

Originally Posted by nirofo

I wouldn't dare rely on keeping all my thousands of scanned images, totalling hundreds of gigabytes, on a hard drive of any description. In the course of a year I repair and maintain many computer systems, some with large hard drives, some with raid arrays, the majority of these come in with some kind of hard disk fault! Sometimes it is quite easy to save the files stored on these disks to a CD or a DVD, slap in a new drive, re-boot the system and everything's fine. Then there are the drives that are completely trashed for one reason or another, normal file restoration and saving with these drives if not impossible can be extremely expensive, usually entailing a trip to a specialist data recovery company. In either case the average computer user doesn't want the hassle and certainly doesn't want the cost! I backup my scans and digital images on a regular basis, I scan and process 10 then save to DVD-R using Nero Burning Rom or Nero Express. Working this way the most files I can lose will be 10, it only takes a few minutes to burn 10 images to DVD, it can take hours to scan and process in Photoshop 10 images to the computer.

nirofo.

The problem with that, in my opinion anyway, is that writing DVD's is a right royal pain once you have a lot of data, and cannot be done unattended, whereas a HDD to HDD backup can be automated. Unfortunately DVD's don't last that long so you need to make further copies at regular intervals, adding to the inconvenience.

No medium is fault free, but for me an external HDD is the most convenient method at a reasonable price. High speed tapes seem to be favoured by companies though they cost a bit more at least at the outset. I think that for really large amounts of data they work out cheaper.

[Leif]

Originally Posted by Tannin

This depends on three main factors:

1: The way the drives are handled, both in the wharehouse/distribution channel and by the installation technician. Hard drives are very sensitive to shock, and although a nasty bump very rarely shows up with an immediate failure, it greatly increases the risk of failure later on. Many people don't fully realise this and pay only lip service to what is, in reality, the #1 rule of hard drive safety - treat them like they were made out of eggshells! This is why we only ever buy drives from a known and trusted distributor with a track record of doing it right, and even then always buy more than 10 units at once. (Hard drives come ex factory in boxes of 20. If you order 5 drives or 9, the warehouse guy takes them out of the box, maybe packs them properly, maybe doesn't, maybe bangs them down on his desk, maybe doesn't, then ships them to you. If you buy (e.g.) 15 drives, human nature being what it is, the warehouse guy takes the other five drives out of the box and your 15 stay nice and safe in the factory carton, which is proof against even couriers and truck drivers. Best, of course, is to simply buy a box of 20.) Obviously, you don't want 20 hard drives - but you can buy your drive from someone who does buy them that way, and who knows how important it is to look after them.

2: The quality of the drives used. There are major differences in reliability between different brands of drive. Seagate/Maxtor and Western Digital drives have a failure rate measured in units per hundred, typically a modest single-digit number per hundred, but higher for a bad model. Samsung drives have a failure rate measured in units per thousand, and it's a small single digit. I don't see enough Hitachi drives to put a number on their RMA rate, but it's probably closer to the Samsung figure than the Seagate/WD one. (Just guessing on this last.)

3: Clint's Rule. ("Do I feel lucky?")

Which can be summarised as "Hard disk crashes are not that rare".

Do you have a source for your HDD failure rates? I'd assumed that HDD's are pretty much of a muchness, but if as you say there are large differences in mean time to failure rates, then obviously it's worth avoiding certain makes.

Leif

[nirofo]

As I said earlier, I receive many computer systems for repair that have some form of hard drive fault, I would say it's probably as high as 90%. The majority of these are caused by hard drive crashes which occasionally can be repaired, but more often than not will lead to further problems in the not to distant future, the rest are catastophic hard drive failures! Usually, the best and safest remedy means a new replacement hard drive and a complete system re-boot. In some cases the data is recoverable from the old hard drive without too much effort or expense, in others the monetry cost of data recovery is outwith the majority of general PC users. Bottom line, for fast, easy storage that you could lose catastrophically at any time, go for large hard drive storage (internal or external). For long term safe storage, albeit with slightly more involved file saving methods, go for DVD-R. The longevity of DVD-R disks is supposed to be in the order of 25 years, providing you still have the PC's and drives to use them. I'm not sure what the storage longevity of say a 200Gb hard drive is drive is, (it's magnetic media), and you still need a PC to run it even after 25 years. Price of 40 x 5Gb DVD-R disksm (200Gb) approx £20, price of one 200Gb hard drive, (40x5Gb DVD-R disks) approx £70. Oh yes, and I can watch films on a DVD player-recorder.

nirofo.

[Leif]

Originally Posted by nirofo

As I said earlier, I receive many computer systems for repair that have some form of hard drive fault, I would say it's probably as high as 90%. The majority of these are caused by hard drive crashes which occasionally can be repaired, but more often than not will lead to further problems in the not to distant future, the rest are catastophic hard drive failures! Usually, the best and safest remedy means a new replacement hard drive and a complete system re-boot. In some cases the data is recoverable from the old hard drive without too much effort or expense, in others the monetry cost of data recovery is outwith the majority of general PC users. Bottom line, for fast, easy storage that you could lose catastrophically at any time, go for large hard drive storage (internal or external). For long term safe storage, albeit with slightly more involved file saving methods, go for DVD-R. The longevity of DVD-R disks is supposed to be in the order of 25 years, providing you still have the PC's and drives to use them. I'm not sure what the storage longevity of say a 200Gb hard drive is drive is, (it's magnetic media), and you still need a PC to run it even after 25 years. Price of 40 x 5Gb DVD-R disksm (200Gb) approx £20, price of one 200Gb hard drive, (40x5Gb DVD-R disks) approx £70. Oh yes, and I can watch films on a DVD player-recorder.

nirofo.

Nirofo: I don't doubt your experiences with hard disks, but I do doubt the figure you give for the longevity of DVD. Many CD's will last no more than a few years, and there is a huge variation in quality. A friend found that PCLIne CD's delaminated within a year or two. Some online test reports I saw found that they did not last as long as the manufacturer's implied. There are only a few CD manufacturers, and most CD's are in fact rebadged. It is sometimes possible to determine the original manufacturer by examining the CD or using Nero to read CD meta-data. I think the best include Memorex, Fuji and Ritek, but even big names will re-badge poor quality disks. I had huge problems with Phillips disks and had to take them back to the shop.

And of course disks need to be stored in a cool, dry and dark place.

I am not too sure about DVD, but I would guess that it is worse than CD. I presume the technology is in essence the same, but with smaller pits, and higher rotation rates, and hence the tolerances are tighter, meaning more likelihood of failure.

Here's a few links I found from a quick google:

http://www.cdfreaks.com/news/12933
http://www.cdrfaq.org/faq07.html#S7-3

Sorry but I can't find the report of accelerated aging tests that I read some time ago.

Leif

[nirofo]

I've got CD's going back to 1994, they still work perfectly, but then I store them correctly and only use them when I really need to, I catalogue all my files and CD's so that I can find the image I want without having to subject the disks to strenuous searches and handling. For most people I would think infrequent use for stored images is the norm. I have several hundred CD's with images and other data on them, I haven't lost a disk yet unless I did something stupid myself. I now use DVD-R disks, been using them for about 18 month's now, no problem so far! In the last ten years I think I've probably gone through 8 or 9 of my own hard drives, some of which cost a fortune when they first came out. I've lost many files and images from hard drive crashes and breakdowns over the years. I'll continue using DVD-R until the next generation of high definition disks become available at sensible prices. I keep a couple of old computers in my loft, fully set up and able to run any of the disks I have at present, all my images are saved as TIFF files so any of the graphics programs, past, present and future will handle them. I also have a couple of spare DVD reader drives in case of emergency (cost £11.50 each new), these are adequate for reading any of the files or images I own and will keep me going for years to come.

nirofo.

[robski]

Originally Posted by nirofo

In the last ten years I think I've probably gone through 8 or 9 of my own hard drives
nirofo.

Have you been unlucky or have I been lucky ? In 18 years I've had 2 go. I have never bought a new drive they have always been pre-enjoyed. I have 2 drives in my machine. From my experience of our customers systems drives typically last 5 year before you see the operating system complaining about disk problems.