
Ask HN: What is more reliable, a DVD or an Hard drive? - federicoponzi
For long term backups, how do you (if you do) handle them?
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cimmanom
Hard drive failure modes are more likely to be recoverable.

The most common failure for a DVD (other than scratches) is physical
degradation of the storage medium, which makes the data corrupted and
completely unretrievable, if it can be read at all.

A spinning disk is most likely to fail because the moving parts get locked up.
In a pinch, data retrieval specialists can move the platters to a new drive
and be able to read them again.

Magnetic hard dives do sometimes experience spontaneous data corruption, but
it’s much less common, and typically corrupts only a file or two (a flipped
bit here and there) rather than making the entire drive unmountable. The
exception is if you expose your drives to stormy magnets, which... we’ll, you
don’t do that, do you?

I’m less familiar with SSD failure modes - perhaps someone else can speak to
that.

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DanBC
> In a pinch, data retrieval specialists can move the platters to a new drive
> and be able to read them again

Can you link to any company offering this service please?

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cimmanom
Not off the top of my head, but any good data recovery shop should either know
how to do this or be able to refer you to someone who does.

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kristoff_it
Writable DVDs degrade pretty quickly as they are made of different materials
compared to the ones you buy with software/movies already printed on them.

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jolmg
I would think that the best option is a RAID 1 with hard-drives and a
filesystem that checksums all files and their metadata, like btrfs or zfs. I
believe these filesystems support recovery via RAID 1 setups. It's just a
matter of periodically (automatically) asking the filesystem to verify all
files with their checksums and fix whatever corruption it sees with the hard-
drive that has the good copy of whatever was corrupted.

I would set it up so that it reports whenever it finds errors. Every time a
drive starts to fail frequently (because everything needs to fail at some
point) I would buy a new hard-drive to replace the failing one and clone the
drive that has the good copy.

It might be good to get drives from different (good!) vendors to minimize the
chance that they'll both fail at around the same time, because if that happens
you'd have to figure out from which drive to copy which blocks. Maybe it's a
good idea to make a RAID 1 with more than 2 drives? Idk, that might be going
overboard. Still tons better than DVDs, lol.

EDIT: If you want to go further, it might also be good to sync your backups
with an online service like rsync.net or something. It's more expensive than
local backups because you have to pay rent for the storage, but that way you
won't lose anything if your house catches fire or was robbed or whatever. You
might think that if you did that, then there's no point in having your backups
locally, but I would hope people stop trusting businesses so much (especially
the free ones) with something as important as having the only backups of
family photos and videos, etc. Backups is the kind of thing that never matters
until it's critical.

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amorphous
I lost a lot of holiday pictures ~10 years ago when I used DVDs as my backup
medium. I wasn't aware of how little they last. On the other hand, I have
personally never experienced a hard drive failure.

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brudgers
[for personal data]

The unreliable part of a backup system is the human. Maybe DVD media is more
reliable. Maybe it isn't. Probably it doesn't matter. If all your data fits on
one DVD, then it is practical. If all your data doesn't fit on one DVD, then
it's not...at least for most people[1] -- I think.

For me, I use hard disks. Not really as a explicit strategy [2], but because I
have them laying around. I have them laying around from upgrading to SSD's and
replacing laptops and installing new OS's...new disks are a time efficient way
to upgrade an OS on an existing system. Compared to DVD's storing 100GB of
data on an old 250GB hard disk is easy...or two old 250GB disks. Most of the
time, I don't need old personal data. If I need it, it's ok to have a few (or
many) copies...it's probably better. Short of storing video, HDD far outstrip
most people's personal data needs. As I mentioned, that's still a common case
for DVD's. It's just that DVD's require explicit backup and HDD's don't.

[1]: Anyone who is actually willing in practice to swap DVD's will almost
certainly have already committed to a backup strategy.

[2]: Well ok, I have motherboard RAID mirroring on the tower ...I'd kind of
forgotten about it because the tower is 10 years old and shipped with it.

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imhoguy
Backups (short-term) and archives (long-term to forever) are often two
different things.

For long term archives of selected data I play with Perkeep on local NAS. Also
I burn M-Discs and BD-R HTLs and in general every decade copy all that to
newer and bigger WORM storage.

For backups of NAS against disaster recovery I use offsite SFTP storage
(Hetzner StorageBox). BorgBackup and a bunch of scripts take care of
encryption, dedup and retention.

The point of archive is that it needs to be easy for my grand...grand children
to find and read my box of family photo disks in the under stairs closet. Then
in case of NAS failure I have these fresh cloud backups to recover from.

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linkpuff
I dont usually make long term backups(mostly due to not enough recources), but
the ones I do are to hard drives(internal and external). I dont trust dvd due
to how easily they are scratched

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superasn
Cloud storage is the best way for long term backups, esp established providers
like Dropbox or Google drive.

Also using Amazon S3 or digital ocean spaces is relatively cheap and super
easy to do with tools like s3cmd

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imhoguy
I would use these only for secondary encrypted backup. AWS Glacier is even
cheaper for backups.

