Feeds

You don't know disk about storage failures

Research shows platters a victim of spin

Combat fraud and increase customer satisfaction

Knowing just what breaks a storage box is of obvious interest to data center admins. It's quite reasonable to conclude the blame should be heaped on the 80-some platters spinning all day at 7200 RPMs.

But a recent study presented at the USENIX Conference on File and Storage Technologies argues that disk failure isn't nearly the whole story. Other components in a storage subsystem are often the point of failure, although their failings are still treated as disk faults. This results in unnecessary disk replacements — and inevitably an incomplete perspective on storage system resiliency.

The study, titled "Are Disk the Dominant Contributor for Storage Failures?" was authored by Weihang Jiang, Chongfeng Hu, Yuanyuan Zhou of the University of Illinois department of computer science and Arkady Kanevsky of Network Appliance.

Over a period of 44 months, the group analyzed storage logs of about 39,000 commercially deployed storage systems. They estimate the systems in total were composed of about 1,800,000 disks hosted in about 155,000 storage shelf enclosures. The researchers examined near-line (backup) disks, low-end, mid-range, and high-end hardware.

While the findings do show disk failures contribute to 20-55 per cent of storage subsystem failures, other components such as physical interconnects (broken wires, shelf enclosure power outages, HBA failures, etc) and protocol stacks (software bugs and compatibility issues) also account for a significant percentage of problems.

The group states that recent studies on storage failures have failed due to an excessive focus on disk malfunctions. For example, in June, Google released a paper that disputed the reliability claims of disk manufacturers from a user perspective. A good start, write the researchers.

"But as this study indicates, there are other storage subsystem failures besides disk failures that are treated as disk faults and lead to unnecessary disk replacements," their paper claims.

The research indicates between 27-68 per cent of storage subsystem failures come from physical interconnects. Between 5-10 per cent are a result of protocol stack errors. Due to component failures, even slower, more reliable disks like near-line backup have higher failure rates.

"These results indicate that, to build highly reliable and available storage systems, only using resiliency mechanisms targeting disk failures (e.g. RAID) is not enough," the study states. "We also need to build resiliency mechanisms such as redundant physical interconnects and self-checking protocol stacks to tolerate failures in these storage components."

As an example, in low-end storage systems (defined as having embedded storage heads with shelf enclosures) the annualized failure rate (AFR) is about 4.6 per cent. The AFR for the disks only is 0.9 per cent, or only 20 per cent of overall AFR.

Near-line storage disks (mostly SATA) show a 1.9 per cent AFR, but again the whole storage subsystem failure is higher, at 3.4 per cent.

So, on their own, low-end disks fail less often than higher-end SATA disks, but total SATA systems fail less often than lower-end systems.

The researchers argue this indicates that "disk failure rate is not indicative of the storage subsystem failure rate," meaning there's other factors for failures such as shelf enclosure model and network configurations that strongly affect reliability.

The research team concludes that storage subsystem components cannot be ignored when designing a reliable storage box. They offer some suggestions to improve reliability.

Redundancy mechanisms such as mulitpathing were able to reduce AFR for storage systems by 30-40 per cent when paths were increased from one to two.

The researchers also recommend spanning a RAID group across multiple shelves — and using fewer disks per shelf, with more shelves in the system. This helps reduce the chances of a shelf failure taking out an entire RAID group.

The full paper is available here at the Usenix website. ®

3 Big data security analytics techniques

More from The Register

next story
This time it's 'Personal': new Office 365 sub covers just two devices
Redmond also brings Office into Google's back yard
Kingston DataTraveler MicroDuo: Turn your phone into a 72GB beast
USB-usiness in the front, micro-USB party in the back
Dropbox defends fantastically badly timed Condoleezza Rice appointment
'Nothing is going to change with Dr. Rice's appointment,' file sharer promises
BOFH: Oh DO tell us what you think. *CLICK*
$%%&amp Oh dear, we've been cut *CLICK* Well hello *CLICK* You're breaking up...
AMD's 'Seattle' 64-bit ARM server chips now sampling, set to launch in late 2014
But they won't appear in SeaMicro Fabric Compute Systems anytime soon
Amazon reveals its Google-killing 'R3' server instances
A mega-memory instance that never forgets
Cisco reps flog Whiptail's Invicta arrays against EMC and Pure
Storage reseller report reveals who's selling what
prev story

Whitepapers

SANS - Survey on application security programs
In this whitepaper learn about the state of application security programs and practices of 488 surveyed respondents, and discover how mature and effective these programs are.
Combat fraud and increase customer satisfaction
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Top three mobile application threats
Learn about three of the top mobile application security threats facing businesses today and recommendations on how to mitigate the risk.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.