Welcome to SoftRAID's News and Views page where we feature interesting articles about things that interest and excite us at SoftRAID, along with contributions from SoftRAID customers and guests.
by Tim Standing, VP of Engineering at SoftRAID
February 9 2017
Did you know that storms can break your computer? Most people worry about power spikes caused by lightning. They purchase power strips with surge protectors to prevent power spikes from frying their computers.
A much more likely cause of computer damage is brownouts. A brownout is when the voltage in your electricity lines goes lower than it should. You often see the lights go dim or "brown out" for a few seconds. Brownouts during storms are often caused by tree branches or other objects touching the power lines which bring electricity to your home or business. When the tree branch touches the power line, some of the electricity goes into the branch and the wires no longer have enough power to provide the correct voltage.
Just look at this video clip taken by a member of the SoftRAID team on their way home earlier this winter. There's probably a wet tree branch stuck on the top of the transformer causing all the fireworks.
Most likely, every home and business supplied by that transformer was experiencing a brownout the entire time that tree branch was causing that wonderful light show.
In one year, I lost a computer and 2 monitors during brownouts caused by storms. Then I spoke to an electrician in my town. He explained the difference between voltage spikes and brownouts. While most users purchase power strips with "surge protectors" for their computers, these power strips can only protect against voltage spikes. They are powerless to protect to protect your equipment from brownouts. You need a UPS or power conditioner to protect from brownouts.
I didn't want the expense or maintenance of batteries so I chose to purchase a power conditioner for my computer equipment. Since I first started using power conditioners 20 years ago to protect my equipment, I have not experienced a single failure due to a brownout during a storm.
While a UPS can be quite expensive, a power conditioner is relatively inexpensive. I have been using the power conditioners from APC, their Line-R models in the 1200 VA size which cost about $50.00.
It's not just storms that can cause a brown-out. Any time your circuit is overloaded (a common symptom of which is lights dimming) you could be experiencing a brown-out that could damage your computer or other electronic equipment.
This is really true! A friend of mine in Boston, was never able to have a desktop computer last more than 2–3 years. I figured out the culprit was his attic fan. Each time it started up, all the lights in his house would dim for 2–3 seconds. When I suggested a power conditioner to him, he said he already had one. It turned out he had one which covered his entire house, including the attic fan. It made sure the voltage coming into the house was okay, but did nothing about the huge power draw from the attic fan. So he got a smaller power conditioner for just his computer equipment. That was 4 years ago and he hasn't had a problem since.
by Tim Standing, VP of Engineering at SoftRAID
October 6 2016
A kernel panic is a crash, the type when your computer just freezes—the mouse stops moving and everything on the screen is still. A few seconds later, your computer reboots and you may have lost all the work you had just been doing.
We pride ourselves in fixing 100% of the bugs in SoftRAID which cause kernel panics. We know how disruptive they can be to your everyday life and don't want to be responsible for you losing work.
So I was really troubled 6 months ago when I started getting kernel panics on my development Mac, the one I use to create the SoftRAID product. I had just started using new virtualization software allowing me to run several different versions of Mac OS X on the same Mac at exactly the same time. Since the kernel panics started when I started using the new software, it seemed natural that the software was causing the kernel panics.
At first, I encountered the kernel panics every 2–3 weeks, always after I had run the virtualization software. Then they started happening every week, finally every 2–3 days. It was getting to be a real nuisance.
During this time, Mark James, one of our support engineers, was helping a customer
who was also experiencing kernel panics. The customer said they were happening on his 2013 Mac Pro, while using a RAID 4 volume, created using SoftRAID, and made of 4 SSDs. The customer naturally assumed the kernel panics were caused by SoftRAID because they started occurring after he created his SoftRAID volume.
The interesting point was that this customer only encountered the bug when 64 GB of RAM was installed in the Mac Pro.
We tried to reproduce the problem, using the same amount of RAM (64 GB). However, we could not get the kernel panics to happen. A few weeks later, I asked Mark if he had resolved the issue with the customer. "Yes," he said, "it was bad RAM. Once the customer replaced the RAM, the kernel panics disappeared entirely."
The next day, I purchased replacement RAM for my development Mac. Since I installed it, 6 weeks ago, I haven't had a single kernel panic.
So even though we all want to believe that kernel panics are caused by inferior software, sometimes it is actually a hardware problem—like bad RAM!
At August's 2016 Flash Media Summit (in Santa Clara, CA) SoftRAID’s VP of Engineering, Tim Standing, talked about the challenges around SSD failure prediction.
September 9 2016
Tim started off talking about SoftRAID’s efforts to make storage more reliable: “In 2010, we added a feature for predicting disk failure, which used the results from a Google study on 100,000 rotating media disk drives. This feature can warn users weeks or months before a disk fails. The feature predicts about 75% of disk drive failures, the other 25% of the failures happen without any warning.”
SoftRAID’s success in predicting disk failure in rotating media spurred Tim and his team to develop a similar system for SSDs: “After we saw the power of failure prediction, we wanted to develop the same feature for SSDs."
For those of us who don't know why SSDs can't use the same process as rotating media for failure prediction, Tim explains: "When disks with rotating media are about to fail, they start reallocating sectors. We can use the reallocated sector count as an indicator for impending disk failure; the more sectors reallocated, the nearer the disk is to failure. Unfortunately, this technique doesn't work with SSDs because SSDs reallocate sectors during everyday use—every time a flash memory block stops working, the controller reallocates another block of flash memory to replace it. It's not unusual for a healthy SSD to have thousands of reallocated sectors."
So another technique needed to be used for failure prediction in SSDs, and Tim thought his team had found it: "We were excited to discover that SSDs contain a Media Wearout Indicator as one of their SMART parameters."
Tim then described how the Media Wearout Indicator works: "Remember that SSDs have 10 - 20% extra flash memory (a 100 GB SSD actually contains 110–120 GB of flash memory). This extra flash memory is used to replace flash memory blocks that wear out as the SSD is used. The Media Wearout Indicator displays the amount of extra flash memory still available in an SSD. It goes from 100% when the SSD is new down to 0% when all this extra flash memory has been used up.
However, as Tim went on to explain, the Media Wearout Indicator didn’t turn out to be quite as useful as expected: “We had high hopes that this indicator would provide us with a predictive indicator for impending failure. Two years ago, we incorporated a mechanism for monitoring it into SoftRAID. Since then, we have seen no SSDs which have failed because all their extra flash memory has been consumed. All the SSDs we have seen fail have failed with the Media Wearout Indicator well above 80%. We are still trying to develop a reliable mechanism for predicting when SSDs will fail."
After his talk, Tim spoke to Chris Bross of DriveSavers Data Recovery, Inc., who said that their experience was exactly the same. SSDs fail catastrophically and without warning, and the Media Wearout Indicator is not useful in predicting when they will fail.