Restore often plays the role of the forgotten little sister compared with big brother
who plays the part of Backup.
The mechanical details of a restore are easy, the software provides menu
driven prompts. However, remember that horrifying statistic, 35% of restores are not going to work as
you anticipated. The problems come in
unforeseen outside factors. The best way that I can illustrate what can go wrong with restore is through horror
stories from cases that I have been involved with.
Here is the unluckiest case I have come across. The company did
everything right, tapes were taken offsite, a restore was scheduled one weekend
every 6 months. Each practice worked perfectly. One day came a bolt
from the blue. Literally lightning struck their building and the computer
building was burned out.
Insurance took care of the recovery costs, and in 6 hours the new servers arrived along
with a mobile building and generator. A courier was despatched with backup
tapes, exactly what happened on that flooded road nobody knows, but the upshot
was the courier slid under a lorry. Fortunately the motorcyclist survived,
but the tapes were crushed under the truck's wheels. Naturally, they had other tapes but they were two days old, and they never did recover all the
data.
September 11th, was a terrible disaster. However, by all accounts
recovering computer systems went off without a hitch. I would like to
contrast the Twin Towers disaster with an IRA terrorist bomb which was exploded
on April 24 1993 in London Bishopsgate. In this English disaster only one person
was killed but it devastated the financial computer community.
I was in London at that time and the rumours circulated that the banks had no
backups. Word was they customer services had to phone their clients and ask 'Ah
hmm, exactly how much money have you got in your account?' People smirked and
said, if only they had asked me, 'I would have told them 1 million'. The story
was believable because the banks second question was, 'Can you prove it with the
last bank statement!'
Well, I repeated this story to quite a few clients. Then one day I spoke to
chap from Digital. He listened politely then said 'I was on that case, and you
were not far from the truth'. 'Yes of course they had backups, the assistant
manager had a garage full of tapes. However, the problem was that there
was no machine in the world that could restore the tapes, the VAX machines were
so ancient there was not a compatible machine anywhere.'
Guy
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Often people get in a groove with backup, the job runs, the event log reports
success, the tape looks good, you tick the calendar. But then you
get a new system and you save the data to a new folder on a different partition,
F:\data. However,
Mr Nobody changed the backup to reflect the new path. As a result one day when
you try a restore, there is nothing on the tape from the F:\.
It goes without saying that its not a backup's fault, once again it is a human logic error.
Hardware Variation of Wrong Drive Problem
Hardware incompatibility
When you try a restore on a different machine, the tape is incompatible
with the newer tape drive hardware. (This is a variation of the
Bishopsgate saga above)
Manufacturers are always keen to make improvements and tape drive
companies are no different. What sometimes happens is that in a desire to
backup faster, they sacrifice compatibility with older models. So tapes
backed up by one model will not restore on a newer version.
My last story is amusing in the telling, but was far from funny at the time. The boss
bought a box of tapes and showed the
timid assistant how to insert the first tape into the DAT drive. On the Monday
the
backup worked perfectly. However on Tuesday the operator could not remove the
cassette. So, being timid, but resourceful, they unscrewed the Tippex
bottle and
painted out Monday's date and over-wrote with Tuesday's date.
Guess what
happened when the boss needed to restore last weeks data? All that was on
the tape was yesterday's
incremental backup. When he looked in the box 23 tapes were still in their
cellophane rappers. The restore did a perfect job on the incremental tape,
but it was a management problem that was responsible for the lack of a normal
backup tape.
Reverse Problem - Rambo instead of Timid
Here we have a case of a new young strapping lad wishing to make a
favourable impression. Our new lad found that the backup tape was reluctant
to eject. No problem to our young Rambo - he ripped the tape out, drive and
all! At least with Rambo you knew you had a problem, so many of the backup /
restore faults only show up when the disaster strikes.
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