4 ms·

Why 5000? Personally, I would quadruple that: http://usenix.org/events/fast07/tech/schroeder/schroeder_html/index.html http://usenix.org/events/fast07/tech/sc

by mmt 17y ago

Why 5000? Personally, I would quadruple that: http://usenix.org/events/fast07/tech/schroeder/schroeder_html/index.html http://usenix.org/events/fast07/tech/schroeder/schroeder_htm... http://usenix.org/events/fast07/tech/full_papers/pinheiro/pinheiro_html/index.html http://usenix.org/events/fast07/tech/full_papers/pinheiro/pi...

yardie 17y ago
5000 is just something I made up as an example. What should be done is HD manufacturers should rate their drives up to a certain amount of hours they have tested themselves. I'm not saying the MTBF of drives. But the chances of data integrity along the life of the drive. Like after 5000 hours you will have 99% integrity, 10000 hours is 95% integrity, 20000 hours is 80%, and so on. They same way tire manufacturers rate their tires for so many miles or kilometers. No logical person waits for a car tire to self destruct before replacement. You note the odometer and make a record of when to change them. So you're not the unfortunate schmuck stuck in snow storm with shredded radials. Data storage is the antithesis of good maintenance. Instead of proaction its reaction. You buy and install a drive, wait for it to die, then replace it.
- Tuna-Fish 17y ago
  Actually, I'm not so sure your advice is very good. The likelihood of a drive failing does not linearly increase with it's age. For relatively young drives, the opposite is true -- if the drive has survived a few weeks of heavy use, it is much LESS likely to fail in the future than a fresh drive off a shelf. Tires are changed routinely because they wear -- hard drives don't so much wear as spontaneously fail. Changing them "before failure" costs you money and increases the amount of drives that blow up in your face.
  - yardie 17y ago
    I think this has more to do with manufacturing consistency than anything else. If a hard drive fails in a few weeks than it's quite likely the lot it came from is also likely to fail. Unless something fundamental has changed about hard drives I think my point is still correct. Hard drives are electromechanical devices that also wear; bearings wear, fluids evaporate, and heads hit the platter. They spontaneously fail like light bulbs spontaneously fail. It's not spontaneous at all. If you know a light bulb is about to blow or is near the end of it's life cycle you change it. In the greater scheme of things the cost of the hardware is miniscule compared to the data on it. If drives start randomly blowing up in your face it's time to get a different model. What I'm getting at is we put more care into the maintenance of our cars than we do our data. If you think hard drives are expensive than what do you think of the cost of productivity while an office full of people wait for a RAID to rebuild. Instead of waiting for the inevitable failure wouldn't it be better to cycle old drives on a friday evening when usage is low. RAID6 is just a bandaid on a bandaid. It came about because drives are of the same age when a RAID is built. And start failing around the same time. RAID 5 can recover from one failed drive, RAID6 can do 2. But you are still vulnerable if a 3rd. But this is still reactive thinking, "I will replace them as they fail", rather than using proactive solutions.
  - mmt 17y ago
    For relatively young drives, the opposite is true -- if the drive has survived a few weeks of heavy use, it is much LESS likely to fail in the future than a fresh drive off a shelf References, please.
    - Tuna-Fish 17y ago
      (pdf) http://labs.google.com/papers/disk_failures.pdf http://labs.google.com/papers/disk_failures.pdf results start on page 4.

by mmt 17y ago

yardie 17y ago

5000 is just something I made up as an example. What should be done is HD manufacturers should rate their drives up to a certain amount of hours they have tested themselves. I'm not saying the MTBF of drives. But the chances of data integrity along the life of the drive. Like after 5000 hours you will have 99% integrity, 10000 hours is 95% integrity, 20000 hours is 80%, and so on. They same way tire manufacturers rate their tires for so many miles or kilometers. No logical person waits for a car tire to self destruct before replacement. You note the odometer and make a record of when to change them. So you're not the unfortunate schmuck stuck in snow storm with shredded radials. Data storage is the antithesis of good maintenance. Instead of proaction its reaction. You buy and install a drive, wait for it to die, then replace it.

Tuna-Fish 17y ago
Actually, I'm not so sure your advice is very good. The likelihood of a drive failing does not linearly increase with it's age. For relatively young drives, the opposite is true -- if the drive has survived a few weeks of heavy use, it is much LESS likely to fail in the future than a fresh drive off a shelf. Tires are changed routinely because they wear -- hard drives don't so much wear as spontaneously fail. Changing them "before failure" costs you money and increases the amount of drives that blow up in your face.
- yardie 17y ago
  I think this has more to do with manufacturing consistency than anything else. If a hard drive fails in a few weeks than it's quite likely the lot it came from is also likely to fail. Unless something fundamental has changed about hard drives I think my point is still correct. Hard drives are electromechanical devices that also wear; bearings wear, fluids evaporate, and heads hit the platter. They spontaneously fail like light bulbs spontaneously fail. It's not spontaneous at all. If you know a light bulb is about to blow or is near the end of it's life cycle you change it. In the greater scheme of things the cost of the hardware is miniscule compared to the data on it. If drives start randomly blowing up in your face it's time to get a different model. What I'm getting at is we put more care into the maintenance of our cars than we do our data. If you think hard drives are expensive than what do you think of the cost of productivity while an office full of people wait for a RAID to rebuild. Instead of waiting for the inevitable failure wouldn't it be better to cycle old drives on a friday evening when usage is low. RAID6 is just a bandaid on a bandaid. It came about because drives are of the same age when a RAID is built. And start failing around the same time. RAID 5 can recover from one failed drive, RAID6 can do 2. But you are still vulnerable if a 3rd. But this is still reactive thinking, "I will replace them as they fail", rather than using proactive solutions.
- mmt 17y ago
  For relatively young drives, the opposite is true -- if the drive has survived a few weeks of heavy use, it is much LESS likely to fail in the future than a fresh drive off a shelf References, please.
  - Tuna-Fish 17y ago
    (pdf) http://labs.google.com/papers/disk_failures.pdf http://labs.google.com/papers/disk_failures.pdf results start on page 4.