SAS is the Next Data Center Certainty

While SaaS (Software as a Service) gets most of the press, SAS (Serial Attached SCSI) is finding its way into increasing numbers of corporate data centers. Parallel SCSI is a proven and reliable data transfer standard and serves the data center well, but all good things must eventually come to an end. With U320 parallel SCSI being the last stop on the SCSI roadmap, and with the advantages SAS has to offer over parallel SCSI, SAS is almost a certainty for the industry at large and your company specifically.

SAS has already gained widespread adoption in disk-based technologies. Accelerating this adoption is the move by Dell, HP and IBM to phase out servers with native parallel SCSI interfaces in favor of SAS interfaces. As the new SAS-based servers proliferate throughout the market, this will ultimately drive the need for SAS-based peripherals, such as automated tape backup and archive solutions. The long-term result is expected to be the eventual demise of SCSI-based peripherals.

That does not mean that storage vendors such as Overland Storage plan to phase out parallel SCSI or support for it anytime soon. According to Peri Grover, Overland Storage’s Director of Product Management, the vast majority of the company’s tape automation solutions still are based on SCSI technology. She does foresee, however, an eventual move away from SCSI which is why Overland has begun introducing tape automation solutions with SAS interfaces.

SAS’s combines high-end feature from the fibre channel world and the physical interface leveraged from SATA with the performance, reliability and ease of use of parallel SCSI technology. SAS’s inherent advantages over parallel SCSI include:

  • A roadmap supporting speeds up to 12 Gb/sec.
  • Point-to-point topology for optimized use of bandwidth
  • Built-in termination
  • Easier management with automatic addressing
  • Ability to connect more devices
  • Ability to share multiple peripherals between several servers

For the short term, many companies are likely to use new servers with SAS interfaces for applications where they will provide the most benefit – such as to support email or database applications. The servers that were previously used to host these applications generally have SCSI interfaces and, for a number of organizations, will be redeployed as the new backup servers. As a result, the demand for tape products with SAS interfaces will be slow at first, but as the SAS-based servers proliferate throughout the data center and SAS cabling becomes more standardized, SAS-connectable tape autoloaders and libraries may become the rule rather than the exception.

During this transition from SCSI to SAS, however, there are some steps that companies can take to prepare and make sure interoperability problems do not creep into their environment:

  • Have a migration plan. Gradually move existing SCSI servers and devices to secondary roles, then replace them with SAS compatible equipment as the need arises.
  • Document your data center infrastructure. Bringing in SAS may result in interoperability snags between servers and tape solutions. Quantify which servers currently use which tape drives and how they connect to them. Realize that as new SAS-based servers show up, they may require gateways or older SCSI cards to connect to existing SCSI-based tape drives.
  • Understand your application bandwidth requirements. SAS will ultimately deliver significantly more bandwidth than SCSI, so applications that use SAS hard drives may feed data too fast to SCSI-attached tape drives during backups. While there may be nothing wrong with existing SCSI tape drives, companies need to realize that using SAS in conjunction with some applications could force them to upgrade to tape drives with SAS interfaces sooner rather than later.

Whether you know it or not, SAS has probably already found its way into your data center, especially if you have recently purchased a new server. The good news is the transition to SAS is not occurring overnight nor will support for SCSI go away any time soon. This will give companies time to monitor and respond to this technology shift by navigating away from SCSI to SAS without breaking their budget or any current business or infrastructure processes over the next few years.

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