Hard disk vs. flash storage: The fight of the century?
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Solid-state drives have triggered a revolution in the deployment and usage of data center storage, but such a profound...
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change in a part of IT that had been stagnant for nearly three decades takes time to work out -- especially with inventions coming thick and fast. We can expect a decade of transitions in storage.
The future for hard disk drives (HDDs) is getting bleaker without expectations of a major rebound. The overall malaise in traditional storage array sales is likely to last through 2016, while replacement of arrays with all-flash arrays and solid-state drive (SSD) storage array appliances will reduce sales even more. The latest trends surrounding SSD and HDD technologies will affect everything from vendor choice and purchasing decisions to an overhaul of operations and maintenance standard procedures.
SSD technology advances
HDD sales continue to decline in 2016, with revenues for both market leaders Western Digital Corp. and Seagate Technology down roughly 20% year over year.
Simultaneously, SSD storage array prices are declining. Dell, for example, sells a $300 1 terabyte (TB) SSD, which handily beats the price of a 1 TB enterprise HDD at $500. Prices for SSDs in distribution are slightly lower at 1 TB, taking much of the steam out of arguments that SSDs are more expensive than HDDs for equivalent storage capacity.
Inexpensive Serial Advanced Technology Attachment (SATA) multi-level cell SSDs are just as reliable from a write-wear point of view in Google's data centers as expensive single-level cell drives, according to a study from the Web giant. SATA SSD is likely a future sweet spot for enterprise storage rather than the much more expensive serial-attached SCSI dual-port drives. Dual-porting adds little value in today's enterprise storage configurations, which focus on distributed data integrity rather than a dispersed hardware setup such as RAID.
Technological advances are pushing SSD and HDD capacity and cost comparisons favorably to SSD.
Seagate developed a 10 gigabytes per second (GBps) flash card that meets Open Compute Project specifications, touting it as an option for hyperscale and high-performance data centers.
Hyper-converged infrastructure, which layers intelligent storage and compute with management, virtualization and networking components, uses large numbers of nonvolatile memory express (NVMe) drives with a peripheral component interconnect express fabric. This configuration upsets the norm for high-end computing.
In capacity developments, a 15 TB Samsung SSD beats the largest HDD. Intel's work on 3D NAND drives is setting density records for further capacity increases. The expectation that in 2017 3D NAND will see price parity with bulk SATA SSDs at around $30 per TB doesn't seem so far off.
The 3D XPoint memory technology from Intel and Micron could outperform even Seagate's 10 GBps SSD, and a nonvolatile dual in-line memory module (NVDIMM) version in the pipeline is byte-addressable. The NVDIMM and the partner NVMe SSDs will change storage yet again and probably nail the HDD's coffin shut.
What SDD arrays means for data centers
Don't expect HDDs to vanish overnight, thanks to conservative behavior and legacy applications that can't shift to a new SSD storage array. Expect HDDs to vanish from the new storage array purchasing discussion, however.
Some experts advise a great deal of study, modeling and vendor analysis prior to a long test before selecting an SSD storage array. Others contend that this isn't necessarily true. When it comes to SSD and HDD performance, expect a tremendous boost from SSD. The question for data center purchasing managers revolves around cost per IOPS, or cost per GBps. Features such as compression and port speeds are very similar across the various all-flash arrays.
Perhaps the most difficult issue is whether to buy from a traditional and well-understood vendor, or save money with one of the more established newcomers.
Looking at the data center bigger picture, the end of the storage area network is in sight. With focus shifting from 60-drive HDD array boxes to smart SSD storage arrays with 10 to 12 drives, vendor choices change, especially with so much open source software in the mainstream. Ceph-based appliances will abound, achieving much lower cost per terabyte compared with arrays, while having billions of IOPS per appliance.
Collaborations between SanDisk and Red Hat have drastically improved Ceph's performance with SSD while they plan further major performance boosts.
The first all-SSD data centers are around the corner. These will not only win out on metrics like cost for IOPS and GBps, they will save an enormous amount of power. SATA SSD wattage pulls about 10% of the power used by comparable HDDs. Add to this the smaller size of the storage farm due to compression, and SSD storage is an unquestionably more eco-friendly option. All-flash storage could be useful for backup sites, but cloud backup is also an option that is quickly gaining ground with SMBs.
With data integrity moving to the appliance level as opposed to residing in the drives as with RAID, maintenance changes dramatically. Data center staff members no longer replace failed drives; it's cheaper to overprovision the data center with storage than to maintain drives. That overprovisioning can be delayed until the IT workloads use up available capacity. The smaller appliances and the commonality of the software across vendors means that delaying capital expenditure until the storage is necessary is the best approach, rather than having to buy a 60-drive array and have most of the capacity idle for a year or two.
The HDD isn't yet dead, but the writing is on the wall, so get ready for a brave new world of storage.
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