6 ms·

Summary?

bluecmd 10y ago
Like any paper, this too has a summary: 6. Concluding Remarks This paper presents an extensive characterization of SSD failures using field data.We first show that SSD failure rates in the field can be very different from what vendors specify. Next, we identify and quantify four types of SMART failure symptoms exhibited by the SSDs, and provide characteristics of symptom occurrence, intensity and progression rate. We show that despite their presence, the symptoms alone cannot be a sufficient indicator of failures. We have also studied the impact of multiple provisioning and operational factors across different layers of the datacenter hierarchy on SSD reliability. Many of these factors are individually influencing, and can also interact with each other in complicated ways, to impact SSD failures. We have used machine learning and graphical model based approaches to systematically consider the impact of multiple influential factors towards answering the what, when and why of SSD failures. We believe the insights gained from this paper can greatly influence the design, provisioning and operational decisions for SSDs in datacenters.
- EugeneOZ 10y ago
  I also found this chapter, but they enlisted here only actions they did, but not conclusions they've made.
  - mirimir 10y ago
    See Table 6 and associated text.
SFJulie 10y ago
Compared to HDD SMART yields quite a lot of false negative/positive hence it is proving harder than HDD means to detect failures. Failure rates seems to not fit the models and be a tad higher than expected. Most SSD are reliable, the only problem is they are failing in a way that is tough to detect leading to consequences we may ignore. (falsely positive functioning SSD in operations and we may experience silent corruptions) Given the "too many knobs" of the SSD they can defect in non predictable snowballing effects (chaotic and dramatic). Basically this study confirms that IEEE standards for rating MTBF are to be reconsidered drastically and that our models of failure for SSD are far from totally being well understood and that SSD is in production while all costs are not totally yet known. The Cost of SSD specific failures is not yet known and they urge SSD makers to begin studying the effects of their "knobs" on reliability Even though it is written in a very scientific neutral tone trying not to scare people, it basically can be used as a strong evidence to ban SSD from critical systems. It basically is an heavy blow to SSD industry since it attacks it on the costs model that is based on its expected reliability and says that these drives are basically still an unknown territory when it comes to failures.
- toyg 10y ago
  You start from the common but misguided assumption that "unknowns" are an absolute evil, whereas they are just another risk factor to weigh. You offset the costs of worst-case scenario readiness with the productivity and financial gains of using the tech. If SSDs make your business 2x as productive or 2x as remunerative, the cost of an extra backup or two is simply a blip. > ban SSD from critical systems. That's an over-reaction if I've ever seen one. I guess it depends what a "critical system" is for you. If it's something that has to guarantee high performance under massive load, SSDs are what you need, period. If it's something that has to guarantee 100-year data storage under a mountain, then there might be better choices, but they might not involve spinning drives either.
  - SFJulie 10y ago
    Well, what about a falsely "functioning" SSD in a system with an SLA of 99.999%. Backups may not be the answer. Ok, it may be RAID1+0 but, what about data corruptions? If primary fails, and secondary is "ok" what will be the state of your data? You don't roll back an image when everything is green. The point is that in critical systems according to the SLA or the critical aspect of the mission (flight recorder, medical instruments...) silent failures, silent data corruption may not be ok. However for 99% of the business that is making money out of SSD right now in the world (advertisement, marketing) this is not really a concern. They don't aim at an absolute reliability. Most industry just aim at good enough. Some small islands of IT aims at doing a legally accurate book-keeping. Like banking, accounting, legal electronic archiving for instance... This topic is covered in Signal Processing in the first chapter of the cost of False Positive and False Negative. Security and risk management norms force to enumerate and evaluate the costs and predicting the outcomes of failures in terms of costs. Here, the paper is saying SSD works pretty much fine all the time. But for failure, there is a lot we don't know. How do you evaluate the cost of a risk you cannot compute? And how does another solution that maybe slower rates in risk management with a better failure model that can be better predicted? The scarriest part in the study is the implication that their could be propagation of failures by coupling in certain environment and that some failure could be snowballing. SSD are affected by heat/memory usage, CPU load is affected by failures, heat rises, SSD are more likely to fail .... They are implying that failures can propagate or spread or happen like a contamination. 1 SSD failing alone is already a problem, even small chances of coupling in failures is making the potentiality for a massive failure. Would you take that risk with a SLA of 99.999%?

Summary?

Like any paper, this too has a summary: 6. Concluding Remarks This paper presents an extensive characterization of SSD failures using field data.We first show that SSD failure rates in the field can be very different from what vendors specify. Next, we identify and quantify four types of SMART failure symptoms exhibited by the SSDs, and provide characteristics of symptom occurrence, intensity and progression rate. We show that despite their presence, the symptoms alone cannot be a sufficient indicator of failures. We have also studied the impact of multiple provisioning and operational factors across different layers of the datacenter hierarchy on SSD reliability. Many of these factors are individually influencing, and can also interact with each other in complicated ways, to impact SSD failures. We have used machine learning and graphical model based approaches to systematically consider the impact of multiple influential factors towards answering the what, when and why of SSD failures. We believe the insights gained from this paper can greatly influence the design, provisioning and operational decisions for SSDs in datacenters.

EugeneOZ 10y ago
I also found this chapter, but they enlisted here only actions they did, but not conclusions they've made.
- mirimir 10y ago
  See Table 6 and associated text.

SFJulie 10y ago

Compared to HDD SMART yields quite a lot of false negative/positive hence it is proving harder than HDD means to detect failures. Failure rates seems to not fit the models and be a tad higher than expected. Most SSD are reliable, the only problem is they are failing in a way that is tough to detect leading to consequences we may ignore. (falsely positive functioning SSD in operations and we may experience silent corruptions) Given the "too many knobs" of the SSD they can defect in non predictable snowballing effects (chaotic and dramatic). Basically this study confirms that IEEE standards for rating MTBF are to be reconsidered drastically and that our models of failure for SSD are far from totally being well understood and that SSD is in production while all costs are not totally yet known. The Cost of SSD specific failures is not yet known and they urge SSD makers to begin studying the effects of their "knobs" on reliability Even though it is written in a very scientific neutral tone trying not to scare people, it basically can be used as a strong evidence to ban SSD from critical systems. It basically is an heavy blow to SSD industry since it attacks it on the costs model that is based on its expected reliability and says that these drives are basically still an unknown territory when it comes to failures.

toyg 10y ago
You start from the common but misguided assumption that "unknowns" are an absolute evil, whereas they are just another risk factor to weigh. You offset the costs of worst-case scenario readiness with the productivity and financial gains of using the tech. If SSDs make your business 2x as productive or 2x as remunerative, the cost of an extra backup or two is simply a blip. > ban SSD from critical systems. That's an over-reaction if I've ever seen one. I guess it depends what a "critical system" is for you. If it's something that has to guarantee high performance under massive load, SSDs are what you need, period. If it's something that has to guarantee 100-year data storage under a mountain, then there might be better choices, but they might not involve spinning drives either.
- SFJulie 10y ago
  Well, what about a falsely "functioning" SSD in a system with an SLA of 99.999%. Backups may not be the answer. Ok, it may be RAID1+0 but, what about data corruptions? If primary fails, and secondary is "ok" what will be the state of your data? You don't roll back an image when everything is green. The point is that in critical systems according to the SLA or the critical aspect of the mission (flight recorder, medical instruments...) silent failures, silent data corruption may not be ok. However for 99% of the business that is making money out of SSD right now in the world (advertisement, marketing) this is not really a concern. They don't aim at an absolute reliability. Most industry just aim at good enough. Some small islands of IT aims at doing a legally accurate book-keeping. Like banking, accounting, legal electronic archiving for instance... This topic is covered in Signal Processing in the first chapter of the cost of False Positive and False Negative. Security and risk management norms force to enumerate and evaluate the costs and predicting the outcomes of failures in terms of costs. Here, the paper is saying SSD works pretty much fine all the time. But for failure, there is a lot we don't know. How do you evaluate the cost of a risk you cannot compute? And how does another solution that maybe slower rates in risk management with a better failure model that can be better predicted? The scarriest part in the study is the implication that their could be propagation of failures by coupling in certain environment and that some failure could be snowballing. SSD are affected by heat/memory usage, CPU load is affected by failures, heat rises, SSD are more likely to fail .... They are implying that failures can propagate or spread or happen like a contamination. 1 SSD failing alone is already a problem, even small chances of coupling in failures is making the potentiality for a massive failure. Would you take that risk with a SLA of 99.999%?