Author: Mike Micheletti, Product Manager, LeCroy Corporation
With Serial Attached SCSI (SAS) products now entering the market, IT professionals are evaluating how this new storage architecture can benefit data centers in the small/medium business arena. Cautious about adopting new data storage technology, this IT community needs both a compelling business case as well as confidence in the long term prospects for this new architecture. SAS-based storage vendors are ready to answer these concerns with a value proposition based on performance, reliability and ease of administration that is unrivaled in the storage industry.
Enterprise Class Performance
The first-generation SAS link rate is 3Gb/second (300MB/sec) and supports full duplex data transfers up to 600MB/sec. Based on today’s specs, a 15,000-RPM disk drive will sustain data rates up to 75MB/sec. This means a single SAS link can accommodate up to eight disk drives before saturating a 600MB/sec bus. With Ultra320 SCSI, the bus is saturated after four to five disk drives. So a single SAS link outperforms Ultra320. Plus, SAS introduces the concept of wide ports that allow bandwidth aggregation by combining multiple SAS links together. A 4-wide link can offer up to 1200MB/sec before saturating the system bus. IT managers can justify the investment in SAS storage system based on the superior performance and lower response time it provides for mission critical applications.
Reduced Downtime Saves Money
The SAS interface is interoperable with Serial ATA (SATA) drives at the connector and signaling levels. In the SMB market, using lower cost SATA drives for reference data (e.g., archived records, digital images, etc.) provides companies the flexibility they need to maximize their storage budget. But utilizing SATA drives – with their lower Mean Time Between Failure (MTBF) – can also increase the likelihood of disk failures.
The storage industry has responded with RAID 6. This latest incarnation of the venerable data protection technology, which adds a second set of parity information, allows a RAID 6 system to continue running despite two disk failures. The chance of two concurrent drive failures is increased due to the fact that SATA disks have a failure rate approximately six times greater than enterprise-class SAS drives. The improved reliability, now possible with RAID 6 configurations, more than offsets the slight performance penalty associated with this new data protection scheme.
SAS also provides dual-port connections on 2.5-inch hard disk drives, a feature previously found only on larger 3.5-inch Fibre Channel disks. Dual-port connections eliminate the “single point of failure” found in parallel SCSI. If one host controller fails, the extra data port can maintain uninterrupted communication with a second controller. Small IT shops can now maximize availability of storage resources without the added expense of managing a SAN environment.
Lower Total Cost of Ownership
The ability to install SAS drives for performance or SATA disks for capacity within a single storage infrastructure makes it easy to redeploy assets as business requirements change. In the SMB arena, SAS provides a common architecture that is easier to maintain and manage for busy IT staff. SAS can scale to hundreds of terabytes, yet requires none of the complex administration found in Fibre Channel-based storage networks. Provisioning SAS-based storage is simple for customers and translates into lower total cost of ownership. The increased performance and improved availability with these new storage platforms represent a strong case for SAS in the SMB market.
