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Posts Tagged ‘Tape migration’

Festive fun with LTO

‘Twas the night before Christmas, when all thro’ the house
Not a creature was stirring, not even a mouse;
Save for the IT manager at a German TV channel attempting to restore some footage from their PresStore backup archive in time for a New Year ’s Day TV Show…

To this day we are not sure what was not working, but working it was not. The catalogue of the PresStore backups had been cleared, it was thought that the 200 x LTO4 tapes would no longer be needed, so now a frantic effort was being made to re-create the infrastructure and scan 200 tapes.

With a single LTO4 drive it was already going to be a matter of luck whether the right tape was found in time as even working 24 hours a day you could hope only to get through 40 or so tapes in the time available, and the re-cataloguing kept failing with configuration errors, and so came the call for help, followed by an IT manager in a Volvo bearing LTO tapes and an expression of angst.

One of the benefits of writing one’s own software for various backup formats is that you don’t need to worry about configuration, processing is pretty much a function of tapes drive numbers, and with 20 LTO5 drives running in less than 2 days the PresStore backups had been re-scanned, a catalogue created and the required data identified.

Restoration of the required data from the PresStore backup took about an hour and so with time to spare our hero was racing back under the channel to save the day.

I have no idea who the footage was of, someone I am too old to appreciate I am told, so I apologise now to any Bavarian parent whose New Year peace we were responsible for disrupting, but the happy smiling face of the IT manager made it all worthwhile.

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Unlucky 13?

Being a generally optimistic person and not believing in bad luck, not even if someone turns up with an OnStream cartridge, the prospect of 13 x LTO2 tapes containing ARCserve backups was not of particular concern. Then the additional information was provided, they had been to another company for restoration and there was a problem with the data, the backups were corrupted and could not be restored, “was there anything we could do”?

Not having seen the tapes it was not honest to give more than a cautiously optimistic opinion. No-one here had encountered a corrupted ARCserve backup since some problems with Adaptec 1542 cards and MSDOS with too much memory installed back in the early 1990s. It seemed more likely we would find that they were either not ARCserve at all, or else were encrypted.

When the tapes arrived it all became clear. They were ARCserve with multiplexing, which means that the backup data from several backups can be interleaved and any attempt to proceed in a linear manner without first loading and interpreting the ARCserve MUX (multiplex) tables is going to end in tears, or at least with worthless data. The next challenge was restoration within an average life-span, restoring a single backup would be relatively straightforward one the MUX tables had been correctly interpreted, but with over a hundred backups per tape the idea of restoring one set at a time was not overly appealing as each tape would have to be read over 100 times, effectively turning a 13 tape restore into a 1300+ tape restoration exercise. This is where the benefits of developing software for tape restoration come to the fore, and being able to modify code to enable the simultaneous processing of all backups so each tape took less than 3 hours to read.

Once the tapes had been catalogued the required Exchange email data was located. Anyone fancy a guess at which number tape it was on? Sorry, that would have been too poetic, it was on tape 7.

 

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TK50 data recovery, look out for media degradation

TK50 was a major player in tape backup on VAX/VMS systems several years ago. Being fundamentally ½” (half inch) tape of the type used in open reel drives, but housed as DLT style cartridge, it suffers from the same long term storage problems as some brands of 1/2″ media. TK50 drives could store 70MB of data, and took quite a long time to fill, so have long since ceased to be a viable backup option even if you can find drives and media. But, there are a surprising number of tapes out there with data on them and recent weeks seem to have brought forth a flurry of requests to get data from them, and in one case to copy some. In a high proportion of these cases the data transfer operation has ended up being a data recovery exercise involving considerable work in the lab.

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eDiscovery and the monster in the vault

Past failure cannot be taken as a signpost for the way things will be in the future, so the inability of the US and UK financial regulatory authorities to spot the credit bubble from 20 paces, or the world’s largest Ponzi scheme even when pointed out to them in neon lighting, should not be taken as a sign that regulation can be ignored.

What is almost certain is that these regulatory paper tigers are about to be forced to become real, and with it will come new zeal for enforcing regulatory compliance leading to an increase in eDiscovery and eDisclosure requests.

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Data migration and the curse of multiplexed NetBackup

A bit unfair to single out NetBackup, any format that supports multiplexing can leave similar problems for anyone attempting an archive-wide data migration project. The problem is this, multiplexing involves the interspersing of data from several sources within a backup set. This gives improvements in backup performance but the payback is in potentially degraded restore performance, especially if attempting a complete restoration of data. Why?

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Data migration – making a molehill out of a mountain

It is very easy to accrue data, and with large diverse systems it is very easy to accrue very large volumes of the stuff from a wide range of different places. The problem comes when you want to get the data from this massive archive and onto a new format of tape to be accessed via a new system.

The more complex the system the more pitfalls when attempting to migrate the data. Where data is being streamed from multiple sources a technique known as multiplexing is often preferred as this gives the best use of the bandwidth available for data backup. The problem comes with restoring as each data set is potentially spread across multiple tapes, and the restore process using the originating backup software might well require that each set be restored individually and so you can end up having to read each tape multiple times. This effectively means that if you have an archive of 1000 tapes, you have to read 5,000 or 10,000 tapes to restore everything.

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