The eMag Link Monthly Articles

August Edition

How Long Does it Take to Restore a Tape
Electronic Data Discovery: It's All About Access (Part Two)*

How Long Does it Take to Restore a Tape

There are a number of factors that can individually or collectively affect the data transfer speed of a tape restoration. They are:

The tape technology employed.
The interface technology employed i.e. SCSI or Fibre.
If the tape is compressed or not, uncompressing creates more data for the interface to cope with.
The data block size, large blocks fast, small blocks slow.
The SCSI or fibre adapter card type and setup.
The adapter card firmware.
The operating system driver for the tape unit.
The number of devices that may be connected to the same SCSI bus. It's an arbitrated buss system and will share out available bandwidth.
The file size, open system can create millions of small files, each needs to be catalogued or referenced.
The processor power and adapter card bus speed.
The consistency of the media. Poor media will cause retries and medium /media errors.
The structure of the data i.e. a large single Exchange data base is faster than a brick by brick backup.
The methodology of the backup, striped data or multi server.

Because of the sheer number and complexity of all the above variables its common for many tape restores to take significantly longer than the designed restore/ data transfer speed of the tape device employed. The newer and faster high capacity tape drives and cartridges due to their higher transfer speed can appear be more accommodating in that they are inherently fast, however, they suffer from all the same issues as older drives.

We can however, take a few typical scenarios where many of the variables listed above would fall under what we could call a "typical setup".

Example 1

DLTIV media backed up using a DLT8000 tape drive. A Windows file and print server is backed up. The restore server is a dual processor Pentium with a 160MB low voltage SCSI adapter card with an optimum firmware driver. The DLT drive will transfer data at a maximum speed of 3MB/sec native and 6MB/sec compressed and the cartridge will hold typically 40GB of native data. The software and hardware (i.e. the processor) may prove to be the bottle neck in this scenario as the tape is likely to hold millions of small files and may be written at a relatively small block size typically 32KB At optimum speed the tape will take 3.7 Hours to restore. This will only occur if the drive is allowed to stream the data off the tape. Any errors on the tape which result in a back itch or a retry, or input port buffers overflowing in the adapter card will slow the system down.

Example 2

If we consider one of the later technology drives such as an Ultrium LTO2 drive used in compressed mode. This has been used to perform full backups of large Oracle data base (i.e. large files). The restore server has a number of fibre channel LTO2 drives connected via a 1 GB switch fabric. The switched fibre fabric will at the most transfer on the fabric at 100MB per sec. If a number of drives or other data movement engines are working at the same time then this available bandwidth would need to be shared out among the different users. The LTO2 tape drive will typically compress data in a ratio of 2 to 1 hence doubling the capacity and the data transfer rate across the interface. Therefore this drive would present data to the host server at 70MB/sec. It can be seen that if two drives are running at the same time there is insufficient bandwidth for both drives to run in streaming mode. This results in a reduction in throughput and an increase in restore time. When all the other variables are also considered it can clearly be seen why optimum minimum restore time is seldom achieved.

Typical data restore/transfer time due to the above points

Drive Type	Native cartridge capacity	Drive Native Data Transfer Speed	Theoretical Minimum Data Transfer Time	Typical Data Transfer Time Due to above
DLT7000	35GB	3MB/sec	3.25 Hrs	6.5 Hrs
DLT8000	40GB	3MB/sec	3.7 Hrs	7.4 Hrs
LTO1	100GB	15MB/sec	1.85Hrs	4.0 Hrs
LTO2	200GB	35MB/sec	1.6 Hrs	6.0 Hrs.
SDLT 220	110GB	11MB/sec	2.8Hrs	6.0 Hrs
SDLT 320	160GB	16MB/sec	2.8 Hrs	6.0 Hrs
3590e std length	20GB	14MB/sec	0.4 Hrs	1.0 Hrs
3590e ext length	40GB	14MB/sec	0.8 Hrs	1.6 Hrs
STK 9840	20GB	19/MB/sec	0.3 Hrs	1.0 Hrs
STK 9940	200GB	30MB/sec	1.85 Hrs	6.0 Hrs

Note: Tape restore times significantly different to the above would suggest that either the data is not typical (i.e. the data block size is very small) or millions of small files exist. Alternatively the drive, server, adapter card, firmware etc. is not optimized

Electronic Data Discovery: It's All About Access (Part Two)*

The following articlen was written by eMag and appeared in the May Edition of e-Discovery Law & Strategy.*

Non-Native Restoration at Work: Case Studies

Non-native restoration has been used with great success in a variety of situations by numerous organizations, as these hypothetical examples demonstrate. The examples are common to cases undertaken across the nation.

An international financial institution declared bankruptcy and fraud was suspected. The organization had backed-up its corporate records and communications on Legato tapes, which had been stored in a vault for some years. During that time, all personnel involved in data archival had been released, and all the software and affiliated documentation had been allowed to expire. A number of software companies had been hired to retrieve the data, but had been unsuccessful. Finally, an electronic discovery vendor with a background in non-native restoration was selected to convert the inaccessible data. After cataloging and identifying relevant files, e-mail documents were reconstructed which recreated financial dealings leading to an indictment for fraud. The case is ongoing.

In a case requiring close collaboration with the client, an electronic discovery vendor recently supported an organization that was required to trace documents created and used by a small number of internal custodians. The materials needed to be produced within a couple of weeks. However, the required data was buried somewhere within 50 terabytes of data, the equivalent of trillions of pages of text. Given that an attorney can typically review about 500 pages a day, this amount of data would have required hundreds of thousands of "lawyer days," if approached conventionally. To reduce this overwhelming amount of information, the non-native restoration vendor searched only the headers of the tapes to isolate the e-mails and user files of the selected internal custodians. By defining the required data at the front end - rather than using a two-step process of cataloging the entire archive and then rebuilding each e-mail server to produce the files - the vendor filtered the information and passed along all the unique content to the client. It took less than two weeks to complete the task. Using conventional means, the project had been estimated to take months and cost many multiples more than the non-native approach.

In a similar situation, another customer had stored a pool of almost 1,000 tapes. However, the organization's leadership knew nothing about the systems upon which they were created or what content they contained since they were inherited when the organization was acquired. All information technology personnel from the previous organization had moved on to new employers and all knowledge about the data pool was lost. Because of an ongoing investigation, the new owner was required to produce data from all tape assets. In order to whittle the task to a manageable size, the electronic discovery vendor scanned only the headers of each tape. Performed in just three days for all the tapes, the header scans identified which tapes belonged to which server and which tapes contained e-mail versus user file data. Immediately, the client was able to discount a significant portion of the tapes. As the process continued, the client was soon able to indicate exactly which tapes would be required for full restoration for the investigation, thereby saving considerable time and costs while remaining in compliance with the court order.

In a case concerning the theft of intellectual property, a firm suspected a former employee had stolen research concepts that were developed shortly before that person took a job with a competing firm. After the employee had defected, the competitor introduced a product extraordinarily similar to the original organization's offering. Using non-native restoration, the electronic discovery vendor was able to re-create and analyze a trail of e-mails, Microsoft Word documents and industry drawings that demonstrated with little doubt that the concepts had originated with the client.

Finding the Right Vendor

In cases like these, non-native restoration applications enabled the retrieval of data that would have been considered inaccessible in the recent past. External vendors, armed with tools and resources developed through years of electronic data discovery projects, are able to quickly and cost effectively access data even when no prior knowledge about the host hardware, content, application or format is available.

In fact, these vendors are able to achieve unprecedented results more effectively than internal information technology resources, which are typically scaled to run at 70-90 percent capacity. This makes the task of re-calling and examining significant amounts of data nearly impossible - especially in light of the fact that most legal or corporate investigations require review of between 30 and 50 percent of the organization's historical data.

When selecting an electronic discovery vendor that specializes in non-native restoration, legal and corporate executives recommend considering the following factors.

Established corporate history. Non-native restoration relies upon the ability to access decades-old systems and programs, so vendors must be able to demonstrate years of experience in developing their internal resources. In order to be successful and economical, these vendors must have technological expertise in a broad range of hardware and software, including systems long obsolete.
Consultative and collaborative approach. Corporations often require access to great volumes of stored data. As a result, non-native restoration vendors must be willing to work closely with clients. This allows the two organizations to function as partners to better define the parameters of the project and plan a specific execution strategy - which, in turn, will allow the vendor to produce the appropriate data in the most efficient manner possible.
Confidentiality and customer service. Because electronic discovery projects typically involve legal or corporate investigations, organizations must be confident that the non-native restoration vendor has an incontrovertible reputation. In addition, the vendor must be dedicated to providing the client with superior customer service to ensure data discovery requirements are met or exceeded.
Commitment to excellence. The problems inherent in electronic discovery can be complex and the best vendors are able to call upon creative solutions to overcome even the unexpected. For instance, vendors should be able to deal with damaged media and circumvent impediments that they encounter to achieve full retrieval and restoration wherever possible.

*Originally appeared in Law Journal Newsletters' e-Discovery Law & Strategy newsletter. wwwljnonline.com/alm?edisc.

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