[Info-vax] OT: server farm backups

[Hans Vlems]

Op maandag 29 september 2014 20:41:26 UTC+2 schreef johnwa... at yahoo.co.uk:
> On Monday, 29 September 2014 15:02:14 UTC+1, Shadow  wrote:
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> > On 2014-09-29, CRNG <noemail at atthisdomain.gov> wrote:
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> > > I retired about 15 years ago from being a system manager of a (then
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> > > old) VAX/VMS system.  I did backups to a tape cartridge system daily,
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> > > weekly, etc.
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> > > I noticed a photo the other day of a modern server farm and got to
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> > > wondering what in the world does a company like Amazon use to backup
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> > > the gargantuan amount of data on their systems?  Surely it can't be
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> > > something like tape cartridges.  Does anyone have any idea?
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> > > Just curious about it.
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> > I have no idea but I suspect they just replicate all their data with RAID
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> > and replace disks that die and never really back anything up.
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> > They leave that to the National Basketball Association and their 50 zillion
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> > square mile colo in Utah.
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> > --
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> > NBA email. No signup required! We save all your emails, contacts, phone
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> > calls, disk files and medical info forever. No bandwidth limitations and no
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> > storage quotas!
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> [till a better answer comes along]
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> tldr: Repeat after me ten zillion times: RAID is not backup.
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> You may well be right that cloud vendors offer no guarantees
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> re backups (buyer beware) but RAID isn't backup anyway.
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> Put simply:
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> RAID makes it easier to survive hardware failures and still
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> have an accessible set of data.
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> RAID offers no resilience against finger trouble, application
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> misbehaviour, OS misbehaviour, and the like. In those cases
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> RAID just makes sure that your now-incorrect data is resilient
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> against (some) hardware failures.
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> A separate copy of your important data, perhaps a scheme 
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> involving multiple copies in some kind of suitable backup
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> routine, may give you the ability to restore data. But
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> unless you test the restore, you won't know for sure. It's
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> the restores that matter, not the backups.
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> Amazon used to have writeups on what you needed to do to
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> backup your data when using their cloud. Note carefully:
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> what YOU need to do to backup YOUR data. Maybe things have
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> changed.
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> Here endeth today's oversimplified lesson.

Amen :-)

Indeed, RAID is no backup substitute though many people are tempted to think so.
Especially when making backups meant sitting next to a TA78 and replace reels.
Looking back, I'm guessing here, 3 out of 4 restore operations were, umm, user requests ("Oops suddenly that file was gone").

Hans