[ale] MySQL array based snapshot

[Jim Kinney]

I see your point. First snapshot _is_ complete. Second is only back to the
first, etc. To continue with this, it would require flattening the
snapshots after the copy. With only a single snapshot and assuming an hour
or so of activity, that could be seconds. It could be several minutes in a
high-write db.

I see array as being storage. I don't think mysql has direct disk
access/control like Oracle. I'm 90% certain it requires an OS to manage a
filesystem layer.

On Nov 22, 2016 9:51 AM, "Lightner, Jeffrey" <JLightner at dsservices.com>
wrote:

> The question says “array” which makes it sound like they’re NOT talking
> about LVM snapshot but rather native snapshotting within an external
> storage array (e.g. Thin Image within Hitachi).   Snapshots one has to be
> careful with because often they do not contain all the data from the
> original but only a subset with pointers back to the original and separate
> storage for deltas where the copy the original diverge over time.
>
>
>
> Also the original question didn’t say he wanted this for backup.  It said
> the only results of a web search were thousands of cautioning about relying
> on snapshots as a replacement for backups.   It’s quite possible the
> question has another purpose in mind entirely (e.g. using a copy of a
> database for testing or reporting purposes).
>
>
>
>
>
> *From:* ale-bounces at ale.org [mailto:ale-bounces at ale.org] *On Behalf Of *Jim
> Kinney
> *Sent:* Monday, November 21, 2016 4:39 PM
> *To:* Atlanta Linux Enthusiasts
> *Subject:* Re: [ale] MySQL array based snapshot
>
>
>
> This sounds to me like a LVM snapshot of the database file space.
>
>
>
> http://dev <http://devN>.mysql.com/doc/refman/5.7/en/backup-methods.html
>
>
>
> Snapshot _IS_ a backup as long as it is copied off the original machine.
> Loud google mouths are not always accurate. Dump your Google search cookie
> and see what comes up again.
>
>
>
> There is a STUN event but it's pretty short. The key that I see is to lock
> the DB after a flush (see link) , make the LVM snapshot, then release the
> lock, copy out the snapshot as a backup. The performance drag happens
> during the copy of the snapshot but the copy can be 'nice 20' if things are
> on a decent drive subsystem and drive failure is not expected to be eminent.
>
>
>
> On Mon, 2016-11-21 at 14:45 -0500, Chris Fowler wrote:
>
> I've received this question today and I can't pinpoint on if MySQL
> supports it or not.   Google is flooding me with "snapshot is not a backup"
> pages.
>
>
>
> "Need Processor counts and if the internal DB supports array based
> snapshots which result in minimal STUN of the virtual disk."
>
>
>
> I'm running MySQL 5.X.
>
>
>
>
>
> Chris
>
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> --
>
> James P. Kinney III
>
>
>
> Every time you stop a school, you will have to build a jail. What you
>
> gain at one end you lose at the other. It's like feeding a dog on his
>
> own tail. It won't fatten the dog.
>
> - Speech 11/23/1900 Mark Twain
>
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>
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>
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