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Archive for July, 2009

Data Recovery – Don’t take no-fix for an answer

When I first started in the data recovery industry back in 1995 data recovery was very much a specialist area of expertise. There were no ‘off the shelf’ data recovery software tools. We had to develop our own methods and techniques to get the job done. These days however the data recovery market place is flooded with companies offering such services, so how do you know who to choose?

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Computer Forensics – don’t ignore the tapes

Much Computer Forensic work is associated with data recovery from hard disk drives, USB pens and other common data storage media. Even the television drama departments appear to believe that data is stored only on this limited range of media, I don’t have a back catalogue to check against but I am pretty certain that on Spooks there has never been an analysis of a DLT or LTO tape cartridge. So what about tape? Probably the largest volume of data stored in the world is on tape, so is it of any value in forensic investigations and litigation work?

The hard disk drive in a computer system contains the most up-to date information along with other forensically valuable information such as internet history and local temporary files, so why should you bother looking at the backup tapes?

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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 – whatever happened to optical disk storage?

It is not so many years ago that the world of data storage was buzzing with the development of various optical data storage products from read/write magneto optical disks, ablative WORM and Phase Change optical disk. This was to be the future of high volume, long term archival storage.

So what happened? Back in the 1980’s hard drives were expensive, not much trusted and low capacity. Optical disk offered a far higher capacity, and being a removable media technology, the ability to expand storage by simply using more disks. Tape was then seen as a technology in transition, again not adequate on the capacity front, and there was a perception of reliability issues.

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Data Recovery when everything fails

Much data recovery work involves the salvage of data from one specific type of storage, a hard drive, RAID array, backup tape or DVD. Occasionally a requirement pops up that transcends this norm.

Having faithfully adhered to a regime of nightly backup of a SUN UNIX system, the failure of the hard drive appeared to be an inconvenience that would soon be overcome for this customer. The hard drive having swiftly been replaced, the backup tape was brought back from storage and the restore process initiated. Five minutes in, however, and the DLT drive made a nasty noise, the cleaning lights came on and ufsrestore became ufs-cannot-restore.

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RAID5 backup, why bother?

RAID 5 combines capacity and performance with fault-tolerance, a disk can fail and the RAID will keep on going, so does this mean that there is no need for backup? Is RAID 5 data recovery never going to be a requirement?

Some people seem to think so, but have been dangerously mis-informed. The error correction used in a RAID5 array is there to provide a level of protection for what will often be business critical data, but can still only survive the loss of a single hard drive from the array. Even RAID 6 with double error correction can only cope with a failure of two drives.

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SSD – will hard drives soon be spinning in their graves?

Solid State Disks (SSDs) are being pushed as the next “hot thing” in data storage, so is traditional hard disk drive storage about to be put to the sword?

Well SSDs have been touted as the way forward for many years, the difference now is that the technology finally appears to be developed enough to produce usable products that are not priced out of the general market. It is now possible to replace the hard drive in a laptop with an acceptable capacity SSD without taking out a mortgage, and with lower power usage and greater resistance to shock this is clearly a niche where SSD could well thrive.

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Time someone guarded the guards?

The NHS London “Serious Untoward Incidence Report Summary for 2008-2009” makes rather interesting reading, showing how many minor incidents have resulted in large amounts of data being “mislaid”, potentially in to the hands of persons who would use it for nefarious purposes. You can currently find the incident summary here.

What seems clear is that whilst information storage has undergone a massive technological development, the care of information has been neglected to a shocking extent.

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Hard drive recovery – peeling back the layers

“How many layers of data can you go down on a hard disk drive?” was the question over the phone. Not really a silly question, there is so much mis-information about how hard it is to erase data from hard drives, and how “data-can-be-recovered-even-after-the-platters-have-melted” (possibly the latter is a slight exaggeration).

It is worth debunking the myth quickly. With a hard disk there is a single layer of recordable material on each side of each platter. When an area of this disk is written to, whatever was at the area previously has gone forever. No need to write over it seven times, no need to sandblast the disk.

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