Blog Archives

Tape vs. Disk – It’s Time for a Truce

Over the past couple of years we’ve heard an enthusiastic debate over whether Tape is dead, obsolete, or simply relegated to some secondary role like regulatory compliance or litigation response.  A lot of the “uproar” has been caused by highly vocal deduplication companies marketing their products by creating fear, uncertainty, and doubt (FUD) among users.   And why not, since most of these vendors do not have a significant presence in the tape backup market and therefore little to lose?

However, there are companies with legitimate concerns about managing their backup process and the direction they should take.   They need to understand what the facts are and why one approach would be superior to another.

With this goal in mind, let’s take a look at two popular backup & recovery devices – the LTO-5 tape drive and the 3.0 TB SATA disk, and see how they compare.

  Specification Quantum Internal
half-high LTO-5
Seagate Constellation
ES.2 ST33000651SS
  Average drive cost-per-unit $1,450 $ 495
  Typical media cost-per-unit $54 per tape N/A
  Native formatted capacity 1500 GB 3000 GB
  Native sustained transfer rate
140 MB/s 155 MB/s
  Data buffer size 256 MB 64 MB
  Average file access time 56 sec. 12.16 ms
  Interfaces available 6   Gb/s SAS 6   Gb/s SAS
  Typical duty cycle 8-hrs/day 24-hrs/day
AES 256-bit encryption
AES 256-bit encryption
  Power consumption – Idle 6.7 Watts 7.4 Watts
  Power consumption – Typical 23.1 Watts 11.3 Watts
  Drive MTBF        50,000 hours at          100% duty cycle 1,200,000 hours
  Media MTBF 30-yrs
  Non-recoverable Error Rate 1 in 1 × 1017 bits 1 sector 1×1015 bits
  Warranty 3-Year 3-Year
  Cost Comparison
  Storage Cost-per-GB $0.036 $0.165
  5-year total for 1.0 Petabyte $37,495 $165,330

No surprises here.  Simply doing the math indicates the cost to store 1 Petabyte of data for 5-years would be more four times more on spinning disk than on tape media.  Granted there are other factors involved in the process, but most offset each other.  Both a tape library and a disk array take data center floor space and infrastructure resources.  Both consume power and require cooling.  Each system must be managed by skilled IT specialists.  Deduplication may reduce disk capacity requirements (reducing cost) but so will tape compression and/or increasing the tape drive’s duty cycle from 8 to 12 hours per day.   Surprisingly the only major variable over time is the cost of the media, which is heavily weighted in favor of tape.

In the foreseeable future the 4TB SATA disk will make the above calculations somewhat more favorable for the disk drive.  However, we expect to see the LTO-6 tape drive in production in the second half of 2012, increasing the tape drive’s sustained transfer rate by 30% and tape media capacity by 47%.  This will bring the above tape vs. disk comparison back into close alignment.

The sensible strategy is to develop a backup and recovery system that incorporates both technologies, to capitalize on the strengths of both.   Using disk “pools” to aggregate nightly backups (whether deduplicated or not) ensures backup windows can be met, and greatly improves data restoration time.  Backing up directly to tape from the “disk pools” allows streaming data to be sustained for maximum performance and transfers data to the lowest-cost media available for long-term archiving, disaster recovery, regulatory compliance, and litigation response.

It’s time this argument to bed.  Both tape drives and SATA disk should play a role in a well-designed, highly optimized backup and recovery system.  The “war” is over, and for once both combatants won!

“Big Data” Getting Bigger? Beware of the Ripple Effect…

Everyone seems to be concerned about the “tsunami of data” that is overwhelming the IT world. However, relatively few people appear to be worried about the “ripple effect” of this growth on other areas that are directly or indirectly impacted by this phenomenon.

Storage growth does not occur in a vacuum.   Every gigabyte of data written to disk must also be backed up, managed, transferred, secured, analyzed, protected, and supported.   It has a “ripple effect” that can spread throughout the organization, creating problems and resource shortages in many other areas.

A case-in point is the backup & recovery process.  Every gigabyte stored must be scheduled for backup, so if we’re experiencing a 50% CAGR data growth rate, then we are also subjected to a 50% growth rate in demand for backup & recovery services.  In addition, most companies keep more than one copy of data in the form of supplementary backups, clones, replications, and other forms of duplication.  Therefore a single gigabyte of data can exist in multiple areas throughout the organization.

The ripple effect of storage growth and the areas that are impacted

Areas that are directly or indirectly affected by storage growth.

The picture above identifies at least (36) specific areas that are impacted by data growth.  I’m sure there are others.  Gone are the days when problems could quickly be resolved by “just buying more disk”.

It’s time to “think outside the box”.  This is no longer a localized issue that can be solved by stove-piped departments and back-room technologists.  It is an enterprise-wide challenge that needs the creative minds of many individuals from diverse areas of the organization.  Consider bringing in independent Subject Matter Experts from the outside to analyze complex problems, stimulate creative thinking, and discuss how others have attacked similar challenges.

In today’s world of “big data”, there needs to be far greater emphasis on comprehensive planning, designing in architectural efficiency, minimizing the impact on IT infrastructure, and improving the manageability of our entire IT environment.  Your future depends on it.