Frequently Asked Questions

 How does OptiLink support data integrity?

Data integrity or how we ensure your data is safely managed on optical media occurs at several levels within OptiLink. Data integrity is supported at a hardware level and at a software level.

• Optical media is a very safe media to write to because the read and write heads do not come into contact with the media and they are spaced farther away from the media surface than in a magnetic drive.
• Optical media has a very long stable shelf life, upwards of 50 years.
• All Optical I/O writes by our optical device driver are performed with the SCSI WRITE WITH VERIFY command. When the optical drive writes data it follows up with a read to verify that what was written can be read. Also OptiLink ensures that the area being written to was blank prior to the write.
• Optical I/O isn’t deemed to be successful until the SCSI commands have completed successfully.
• Optical I/O in our products which are closely integrated with a database occur within the context of a database transaction. If the optical I/O fails then the transaction fails
• The physical file system on an optical platter is frequently checked for consistency and can be repaired if necessary. Platters can be corrupted either during manufacturing or by mishandling while on the "SHELF", although this is very rare.
• Objects on our optical volumes can be inspected with our administrative utilities.
• Objects on our optical volumes are described with redundant headers. One preceding the object and one in the directory area of an optical volume.

 How flexible is OptiLink?

For the following reasons we feel that OptiLink is highly flexible:

• The optical and jukebox device drivers automatically configure to the devices which are attached to the server during installation.
• All of the optical devices listed in the "Supported Optical Devices" section are controlled by the same device driver. This means that any combination of those optical sub-systems can be supported simultaneously from a single database server.
• All of the jukebox devices listed in section "Supported Jukebox Devices" are controlled by the same device driver. This means that any combination of those jukebox devices can be supported simultaneously on the same server.
• Your optical hardware and media can be moved from one server to another, UNIX or NT, from one database to another Informix DSA, Informix IUS, or DB2 and with only a change in the OptiLink software your data is still accessible.
• Open/C, our application library interface to OptiLink will work in conjunction with our database extension products for Informix or DB2. This means that C applications can store and retrieve optical objects while the database is storing and retrieving optical objects.
• OptiLink administration utilities allow the system administrator to debug SCSI connection problems and place jukeboxes or optical drives "OFFLINE".

Can OptiLink archive objects?

Yes. OptiLink archive utilities allow volume archiving while the platter remains online; optical I/O and archiving occur concurrently. OptiLink does not require the system administrator to take a volume off-line prior to its archival.

 How fast is OptiLink?

Performance is determined by a number of variables such as database optimization, application performance, and server configuration to name a few. These factors are beyond the control of OptiLink.. But at one site OptiLink running on a SPARCserver 1000 using Solaris 2.5 and a standalone Hitachi 5.25" optical drive achieved I/O rates in excess of 3 megabytes per second.

  High speed through put is achieved because OptiLink

• Allows co-location of large data objects
• Optimizes jukebox robotic arm movements
• Uses the second picker in dual picker jukeboxes for temporary platter storage
• Queues I/O requests and satisfies all I/O requests for the current platter before dismounting
• Enables direct I/O to the application with no intervening data buffers.

Please note that it is next to impossible to achieve the manufacturer’s stated rate of optical I/O. They typically do not test I/O rates with WRITE WITH VERIFY enabled and their test scripts utilize very large data chunks which minimize platter latency issues.

How secure is my investment in OptiLink?

• OptiLink runs on a wide range of server platforms.
• Moving from one database server platform to another requires only a change in OptiLink software, and no changes are needed in the optical sub-system(s).
• Consistency Point Technologies, Inc. is committed to providing quality software and is dedicated to tracking down and solving any problems which arise in the use of its products.
• CPT makes available to its customers regular update releases.
• CPT has a 90 day acceptance period, on receipt of its products allowing our customers time to install OptiLink, configure their optical environment and determine if OptiLink meets their needs.

Can OptiLink perform jukebox backups?

Yes. We have a utility called oparchive and oprestore that supports multi-level, online archive and restore of an optical volume to either a file or tape device. It records the optical objects in the pre-POSIX tar format which allows the UNIX tar utility to be used to extract individual objects to UNIX files. On-line archive allows the writing of data to an optical volume to occur as that volume is being backed up.

Does OptiLink require a separate file-tracking database?

Absolutely not. In the versions of OptiLink which directly integrate with a database, such as Informix, the database itself maintains object type, object descriptions and location of objects stored on optical. With Open/C a handle is returned to the application and the application is required to save that handle for future object referencing. Through the administrative utility opls the location of optical objects can be determined and an object handle derived in case it is lost.

What platform(s) and jukeboxes does OptiLink support?

Refer to the page Supported OS's, Optical Drives, Jukeboxes, and Databases

What interfaces does it support?

OptiLink supports the SCSI interface connecting jukeboxes or stand-alone optical drives to the supporting server.

How much can be stored on a volume or jukebox?

A single side of a 5.25" optical platter can hold from 640 megabytes to over 4 gigabytes of information. A 12" optical volume can hold from 2 gigabytes up to 15 gigabytes of information. A jukebox can store from 16 gigabytes to well over 1 terabyte of information. Total capacity of a platter or jukebox is manufacturer dependent.

What types of media does OptiLink support?

Currently, OptiLink supports WORM and re-writable optical formats on 5.25" ,and 12" and 14" sized platters . Support for CDR is in progress.

Can OptiLink manage more than one jukebox at a time?

Yes. OptiLink can simultaneously manage more than one jukebox and more than one optical drive on the same system. Concurrent large data object I/O and robotic jukebox arm movements is supported for high performance and through put. For example at one site, OptiLink is connected to 3 jukebox sub-systems. Each jukebox is capable of storing 1 terabyte of data and each jukebox is configured with 8 optical drives.

Are there other storage management products this integrated with databases ?

Absolutely not. Only CPT has a database storage focus!

Can OptiLink mix media types?

Yes. Whether or not media can be mixed within a jukebox is more a function of the jukebox than of the OptiLink software. In a jukebox in which all drives are multi-function, we can (and do) support both WORM and re-writable in the same jukebox. In addition, any combination of supported optical storage hardware can be co-resident on a single server to provide the appropriate balance of cost and performance.

Is jukebox partitioning supported?

Yes. OptiLink supports a Family/Volume concept where optical platters are grouped in a set called a Family and platters within the Family are numbered sequentially and called volumes. The fundamental storage unit is the volume and a volume is whatever is mountable in a single drive (whether a single side or the entire platter). The optical system can contain any number of families and any number of volumes within a family.

Can volumes be spanned?

Yes. An optical object can span several volumes but this feature is under control of the application. Large objects can be broken up into sizes that will fit on several volumes and on retrieval specify that several volumes are required. Currently, we have no way of automatically spanning platters.

Can multiple I/O operations be performed?

Yes. OptiLink permits concurrent use of more than one optical drive and optical jukebox. For instance, in a jukebox that has more than one optical drive, reading and writing to those drives can occur simultaneously.

Is the media transportable?

Yes. You can move an optical platter from one system to another and read it (note: there is no intermediate step, such as flushing cached directories, that is necessary). Platters are in a consistent state and can be easily moved to another system without any loss of data. It does require the OptiLink software to be installed on the receiving system.

Where must OptiLink be installed?

The OptiLink Storage Server software is required on each database server system that will be directly connected to optical sub-systems.

Are operations asynchronous?

Yes. Concurrent reading, writing and jukebox robotic arm operations take place simultaneously.

Can you bring jukeboxes or optical drives to an offline state?

Yes. A utility, Opadmin, is provided that permits the system administrator to place a broken drive or jukebox off-line.

Does it do intelligent queuing of access requests?

Yes. To avoid excessive platter exchanges and thus improve read performance, all outstanding requests which were queued when a volume is mounted are satisfied before the volume is unmounted.

Can OptiLink store related data together?

Yes. Clustering or co-location is the placement of related data on the same platter. It is available for performance reasons. For instance, in claims processing, clients requesting benefit reimbursement submit documentation detailing the medical or dental services they received. During the course of adjudicating that claim additional documentation from the client may be required. These documents can arrive for processing over a period of time. For performance reasons, minimizing platter mounting and dismounting can be achieved by locating all of the document images on the same platter. OptiLink supports this by allowing the application to specify which platter large data objects should be written onto.

What file system is used?

OptiLink uses a physical data layout called the Optical File System (OFS) Therefore, data objects are readable on any platform on which our software is installed.

NOTE: The notion that using the operating system’s "native" file system format is safer than using a proprietary format is not true. Use of the host system's "native" file system format is the major cause of hardware/software lock-in. Even with the same operating system, it is possible to have several different (and possibly incompatible) physical file system formats. A case in point is Solaris 2.4. If we set up a file system on an optical platter using a SPARCStation running Solaris 2.4 in the "native" Solaris file system format, that file system cannot be mounted on an Intel-based machine running what purports to be the very same operating system (Solaris 2.4). Also, there is no guarantee that a given operating system provider will continue to use (or even support) a file system with the same physical format in the future.

We know of no operating system that has a "native" file system that can handle WORM platters. There is a hardware "black box" available that can make a WORM platter look re-writable to the operating system. Please note that with WORM media, once the data are written in a particular format, only that physical format can be used to access the data. If the operating system provider abandons that format, it is possible to be left with platters that can no longer be read once the operating system is upgraded. In case there is doubt that this can happen, between DGUX release 2.0 and 3.0, Data General changed the file system format so platters that were set up prior to release 3.0 could not be mounted without first being reinitialized. However, if the platter is WORM, full reinitilization is not possible.

CPT’s physical file format has changed very little since it was first introduced in 1989. It is still possible to read data from platters written on our first implementation. Our platter layout is easily discerned from the file headers that are provided. Several times CPT has provided custom utilities for clients to access data on platters written in alien formats. With simple on-platter data structures, development of these data access utilities is relatively straight forward.

Can offline data be tracked?

Yes, opmounter tracks volumes in standalone drives, jukeboxes, and on the shelf (i.e. off-line). When a volume is exported from a jukebox, it is tracked as "on the shelf."

Copyright © 1997 Consistency Point Technologies, Inc.