

Ask HN: How does Google back up personal data? - kilomanamolik

I'm wondering how Google backs up personal account data stored on their servers (ie, all Gmail messages and attachments, Gdocs files, etc). How do they insure that your data stored on their servers is safe and backed up?  What's the likelihood of losing all the data from your Google account?
======
btilly
The last data loss incident that I'm aware of involving gmail was in 2006,
when a bug in Firefox allowed a cross-site scripting attack to delete emails.
See
[http://www.oreillynet.com/xml/blog/2006/12/gmail_disaster_go...](http://www.oreillynet.com/xml/blog/2006/12/gmail_disaster_google_confirme.html)
for some discussion of it. If anything more recent has happened, it didn't
turn up in a Google search.

Keep in mind that only about 60 users lost emails in that incident. I believe
the accounts were later restored from backup. And the cause of the data loss
was outside of Google. I've never heard of Google itself losing any user data
that was stored in gmail. Ever.

That said, there is a first for everything. Plus, very rarely, accounts can
become temporarily unusable. (The data is safe, but temporarily inaccessible.)
This usually fixes itself in a period of minutes to an hour. I would
personally bet that the odds of your being unable to access your account
because of a problem on Google are significantly lower than the odds of your
being unable to access the internet because of a problem with your ISP. But if
you are concerned, then by all means you can use IMAP to download all of your
gmail data and back it up for yourself.

Note, I work at Google, but not on anything related to gmail. Nor do I
personally know anyone on the gmail team. I only know about the incident above
because I googled "gmail data loss" and it was the only story that turned up.
I know something about how we backup data, but I'm not at liberty to discuss
it. However I will say that I personally have great trust for Google's backup
procedures.

------
wmf
In general, don't expect Google to answer any questions about how they do
things.

I suspect that they don't back up per se but instead replicate data across
multiple data centers.

------
ra
I've never worked for Google, but I understand from reading that BigTable is a
storage service that includes replication.

Here's an interesting post about AppEngine which I expect applies to gmail.
gdocs etc...

[http://googleappengine.blogspot.com/2009/09/migration-to-
bet...](http://googleappengine.blogspot.com/2009/09/migration-to-better-
datastore.html)

