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the cost for gigabyte of hard disks (3.5 SATA) is smaller than bluray one (I am referring to 50 GB disks).

What are advantages and disadvantages of using hard disk instead of read only optical disks?

I am interested in the intrinsic properties of these devices, not external (ie I do not care a 1000 GB HD can store as 20 BD so it requires smaller space).

What I can think right now: - Ease of handle: HD sensible to static electricity and magnetic fields, while optical disks can be scratched and heat can damage them. - Durability: how much time an HD can sit unused and keep its data? I have not data about durability of bluray disks, someone has? (some DVD after 5 years start giving problems in external region)

Other considerations?

Thanks

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12 Answers 12

Disks=faster, cheaper, larger capacity

Optical=data should last longer

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HDD = Moving parts = eventual crash Optical = longevity (IF stored properly) –  KPWINC Jun 5 '09 at 21:05

I've been using hard disks as backup media for at least 6 years. I've used hard drives 20 years old that still have no problems with data retention. The only problem I've had is storage. It's best to put them in a box or case so they are easier to stack and label.

WiebeTech has a good solution: http://www.wiebetech.com/products/cases.php

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Thanks for the link. Will definitely buy a bunch. –  kentchen Jun 5 '09 at 21:00

I'll add to chopper and state that unless your backup requirements require you to keep backup media rotations of years or permanent storage, then either will probably last for the life of your backup rotation.

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Some data (documents for example) must be stored in an immutable form. You can't beat some sort of WORM or optical system can't be beat. If that requirement doesn't exist for you (check with your legal department and any records managers you may have) I think you can't beat a hard disk.

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I would be careful about assumptions on the lifetime of writable or rewritable optical media. I actually had a case where I needed to restore a 4 year old CD-R/W and found that it was unreadable on the drives we had at restore time. The original drive that wrote it was long gone. This was an important back-up, and a restore was tested after it was burned initially. I have not checked what the current life expectation is on optical media, but since then I have only used optical media as a secondary back-up to a separate HD on important archival storage.

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Are you talking about data backups or data archival? These are two related but different problems.

Questions to ask yourself when choosing a solution for backup.

  • How fast do you need to be able to restore data?
  • Do you need point in time snapshots of your data or just the latest?
  • What volume of data are you dealing with? A few TB's would likely have a different solution than a few hundred TB's.
  • And as Jim brought up are there any legal issues involved that would require immutable data.

It sounds like you're not dealing with terabytes here if these are your choices.

But I would vote on external hard drives if you follow the following guidelines. But the first one applies to any backup media.

  • Always have the data on at least two drives and preferably in two geographic locations.
  • Every 3-4 years replace your drives with newer larger drives. You'll be able to consolidate the number of drives your dealing in the process assuming that you're going beyond a single drive.
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Other than the requirement stating that the data stored in media cannot be written, hard disk is always my choice.

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I would go with hard drives since they are more flexible and are cost effective. Also optical media may become a pain to manage and keep organized.

A hard drive should last a long time, just remember to store them inside a antistatic bag and spin them once in a while just to be nice (personal recommendation).

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It is not listed in the question, but one other option that may or may not work depending on your situation is storing it with a service like Amazon S3. Then you don't care how they store it, they do and I bet the costs would end up being less. Keep in mind that if your data needs to be encrypted legally (and even if it doesn't you may want to anyways) you will need a process in there for that as well. I know there are other online backup options out there besides S3. Other Server Fault people, leave their names in the comments, heck there is probably a question with the "what is the best online backup service" somewhere already.

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In my previous job, our most common backup/archive method was using harddrives. the only "difficult" part for us was managing what was saved on each disk. if you come up with some kind of logical/manageable system for organizing your hard-drives you should be golden.

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I think that using hdd's is going to be a good and cheap way for backup, as long as not internal hdd's are used.

Normal Harddisks should last long enough for most needs, on special long time needs you should consider using SSD's or other flash-storage.

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I am not ready to trust flash for any important backups. –  Dennis Williamson Jun 6 '09 at 0:11

I wouldn't feel comfortable backing up data on consumer grade drives...Maybe a netapp or an xiv but then your cost savings go out the window..

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