Spectra Verde DPE Takes on Shingled Magnetic Recording for NAS

Spectra Logic’s newVerde DPE, digital preservation for enterprise, is aShingled Magnetic Recording-based NAS disk platform based on the company’s Verde NAS product. This new platform also comes at a much lower price than usual for bulk NAS storage.

SMR, is a fairly recent process that increases drive storage capacity by allowing each written disk drive track on a platter to overlap the previous track in the same way that shingles on a roof are laid down, increasing storage density by an average of 25 per cent, according to Spectra. Used with Spectra’s implementation of ZFS software RAID, SMR can increase the longevity of long term storage for enterprise.

The Verde DPE product is purpose-built forbulk storageandarchiving. It is best suited forunstructured data, large files, random reads, bulk deletesandinfrequent changes. Customers using it, for example, for general IT shared drive, large bulk archive of research data as well as video surveillance and media archiving may find that, at the same price, they can keep more data for a longer time.

In contrast the current system,Perpendicular Magnetic Recording, PMR, uses a parallel track layout. SMR has the potential for substantial overall hard drive capacity gains by decreasing the space between tracks. The end product physically resembles a regular PMR drive, but with higher capacity in the same physical footprint. However, the different architecture makes the user's experience in terms ofperformance quite different.

PMR can cause problems whenscaling drive capacity, partly because manufacturers try to reduce the size of the write head to support more tracks on a platter. A smaller write head means a smaller write field, which may be insufficient to change the magnetization on the media and preventing the write from occurring. However in an SMR drive, the writer head is designed to be larger, meaning it can magnetize or write the media without affecting readability or stability.

Nevertheless, the SMR layout may introduce a different kind of problem. Because the write head is wider than a single track, data must be writtensequentiallyto an SMR hard drive to prevent destroying the data on the overlapping tracks. If the existing file system isn’t already used to being restricted to writing sequentially to hard disk drives, a management layer has to be set up to convert random writes to sequential writes.

Spectra logic Verde DPE uses a combination ofRAID Z3, continuous data integrity verification and automatic rebuild to global spares to help reduce the probability of data loss when problems arise. It also allows users to mirror data to a second location, providing disaster recovery and remote replication. Due to SMR, Verde DPE can supply one of the highest capacity disk systems now available, about over 7.4PB per rack or 180TB per rack unit, and relatively low power consumption.

Spectra’s ZFS implementation takes advantage of SMR for bulk sequential writes to increase performance, similar to writing to tape. Continuous datachecksum verificationskeep undetected bit error rate at a very low level and a portal to tape is built-in through Spectra’s BlackPearl deep storage gateway.

Verde DPE has a simpleuser interfacefor setup and management. With the front panel Visual Status Beacon LED, users receive real time visual status of the unit for diagnostics and troubleshooting. The Verde DPE NAS scalability supportsdisk expansionin 200TB increments for up to 7.4PB in a single rack. Using 96 drives within 4U expansion units, for example, density of up to 180TB per rack unit can be achieved in a small footprint. Spectra Logic’s intelligent rebuilds and built-in global spares also apply to Verde DPE, with SpectraGuard Support options. www.spectralogic.com