{"id":1096,"date":"2009-09-30T08:06:52","date_gmt":"2009-09-29T22:06:52","guid":{"rendered":"http:\/\/nsrd.wordpress.com\/?p=1096"},"modified":"2018-12-12T15:35:27","modified_gmt":"2018-12-12T05:35:27","slug":"copies-and-backups","status":"publish","type":"post","link":"https:\/\/nsrd.info\/blog\/2009\/09\/30\/copies-and-backups\/","title":{"rendered":"Is a “copy” a “backup”?"},"content":{"rendered":"

There’s been of discussions on various<\/a> storage<\/a> blogs<\/a> both previously, and again now on whether a copy (e.g., a tarball, or a snapshot, etc.) is a backup. There have been arguments on both sides of the fence, and I’m going to equally contribute to those arguments now.<\/p>\n

You see, a copy is<\/em> a backup, and it’s not<\/em> a backup.<\/p>\n

It’s almost like Schr\u00f6dinger’s Cat<\/a> – it may be a backup, or it may not be a backup, and you won’t know for sure until you look more closely at it.<\/p>\n

In my book, I set out early in the process to define a backup<\/em>, and define it as follows:<\/p>\n

A backup is a copy of any data that can be used to restore the data as\/when required to its original form. That is, a backup is a valid copy of data, files, applications or operating systems that can be used for the purposes of recovery.<\/p><\/blockquote>\n

So it would seem then that I come down fairly heavily in favour of the notion that a copy is a backup. Well, yes \u2013 and no.<\/p>\n

In the broadest sense of the term, a random copy of data such as a tarball, an rsync, a zip file, a read-only snapshot is<\/em> indeed a “backup”, as it can be used, in a single instance, for the purposes of recovery. However, so too could be a binary print-out\/dump of the exact state of every bit on a LUN. Few would argue though that such an arduous and manual re-entry process would really be recoverable, even though in theory it is.<\/p>\n

The reason that it’s not really recoverable is we’re all aware of the time frames required for recovery \u2013 recoveries must be completed in a timeframe that is useful to the business (or the end user) who needs the data back. Without that, we don’t really have a backup at all \u2013 just a random copy of the data.<\/p>\n

If we look past the broad term “backup” though, and actually evaluate the term backup system<\/em>, then I would suggest that a single “backup”, unless it’s an instantiation of protection from the backup system<\/em>, is not a backup at all, but instead is just a random (or pseudo-random) copy.<\/p>\n

To me this boils down to the need to work with the notion of Information Lifecycle Protection<\/a>. As you may recall, in a previous blog entry I suggested that there’s a need to break off data protection activities from ILM and define a new process that revolves around keeping data available in order to be managed by ILM. It may seem a small distinction, but it’s one which helps in these sorts of discussions. At the time I suggested that conceptually, ILP may be represented as follows:<\/p>\n

\"Components
Components of ILP<\/figcaption><\/figure>\n

Under this definition, we can cease to worry about whether a copy is a backup, because clearly, a copy will be part of an overall ILP strategy<\/em>. It’s still data protection, but it doesn’t have to be backup<\/em> in order to be data protection.<\/p>\n

My personal opinion is that a single, isolated copy is technically a backup, but is logically not a backup. “Technically is” because it can be used to restore data. “Logically not” because it’s not in itself a guarantee of a correctly designed backup system<\/em>. I.e., unless we can say that the copy came from the backup system<\/em>, we can’t be guaranteed it’s a backup.<\/em><\/p>\n

One last quote from my book \u2013 this time from the back page:<\/em><\/p>\n

A well-designed backup system comes about only when several key factors coalesce: business involvement, IT acceptance, best practice designs, enterprise software and reliable hardware.<\/p><\/blockquote>\n

So the answer I guess to “is a copy a backup” is another question \u2013 “did the copy from a backup system?” If the answer to that<\/em> question is yes, then the answer to the original question is the same. If the answer is no, we can’t reliably answer “yes” to the original question.<\/p>\n","protected":false},"excerpt":{"rendered":"

There’s been of discussions on various storage blogs both previously, and again now on whether a copy (e.g., a tarball,…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[5],"tags":[138,257],"class_list":["post-1096","post","type-post","status-publish","format-standard","hentry","category-backup-theory","tag-backup","tag-copy"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t