FAQ: All about SSDs


Computer Technology Review – Q) What is an SSD and how does it work?

A) A solid-state drive (SSD) functions like a hard disk drive (HDD), except that it uses flash memory instead of spinning disk to store data. With no moving parts, SSDs are inherently more durable and consume less power than traditional HDDs. As there are no mechanical delays, they enjoy significantly lower access time and very little latency. In fact, SSDs offer performance improvements of 280X over SATA drives and 100X over Fibre Channel (FC) drives. Current-generation SSDs have no read cycle limits and a write life cycle of at least 140 years with manufacturers suggesting a 10 year life expectancy. Thus, when deployed properly SSDs will outlast the useful life of a typical storage system.

Q) How do SSDs improve existing storage solutions?

A) Many types of application software (transaction processing, batch processing, query or decision support analysis) can benefit from the super-fast access times SSDs offer. Adding a small amount of SSDs to an environment can result in a significant performance improvement and eliminate a major performance bottleneck for an application, while dropping power requirements significantly.

When deployed in a storage system, SSD drive shelves can deliver performance gains of more than 16X that of SATA drive shelves and 5X of FC shelves.

On the power savings front, if a single brick of SSD is deployed instead of four bricks of 15K FC drives, users can save up to 1045 Watts per hour. The four FC bricks, under load, use 1232 Watts per hour and the single SSD brick uses only 186.6 Watts per hour, resulting in a difference of 1045.4 Watts.

The performance and power savings advantages are undeniable.

Q) Is it possible for storage vendors to guarantee the performance of an SSD?

A) For some vendors, absolutely. By placing only high-priority data on SSDs, it guarantees that only those mission-critical applications will use the SSD capacity. Layering Quality of Service (QoS) on top of the shared disk pool will ensure that low-priority data will not impact the performance of I/O’s targeted for SSDs. QoS provides guaranteed resources for applications and does not allow lower priority applications to steal resources and performance from higher priority ones. Vendors that already have utilization and performance guarantees in place are better able to extend current guarantees to include SSDs.

Q) What are the disadvantages of SSDs?

A) Traditional storage architectures still suffer from their first-in first-out models. This means that SSD I/O’s will become trapped behind slower SATA and FC I/O’s. Pillar’s architecture, which was designed around QoS to support technologies like SSDs, limits the bottlenecks whether it’s SSD, FC, or SATA. All other storage systems on the market today treat these very different drive types equally, thus negating in large part the benefits of SSDs.

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