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SSD Reliability
Ken in Regina
Here's an interesting article about real-world SSD reliability.

http://www.zdnet.com/article/ssd-reliability-in-the-real-world-googles-experience/?tag=nl....e539&ftag=TRE17cfd61

...ken...
tcassidy
A very confusing article. I hope he expands on it in the near future to give a more meaningful explanation of the results. I use SSDs as the o/s drive on almost all my PCs.

Terry
Ken in Regina
Terry, what was it in the article that left you feeling confused?

...ken...
tcassidy
I guess I am confused by what he means by losing data.

Terry
Ken in Regina
If the UBER (unrecoverable bit errors) on a file are too high the file will be unusable, thus "lost".

So:

1.Conventional hard drives fail sooner than SSDs, therefore total drive loss is the bigger concern.

2.UBER (unrecoverable bit error rate) is a much larger issue on SSDs than on hard drives so the chances of losing some data, rather than the entire drive, is the bigger concern.

Since SSDs have chances of losing small amounts of data more frequently, I assume that's why he recommends more frequent backups on them.

...ken...
tcassidy
Sounds like a meaningless steaming pile of BS to me. As you have no control of which file might be affected, it doesn't matter if you lose the whole drive or only a portion of it. Regular backups are the only solution in either case.

I don't use SSDs because they are more reliable. I use them as they are faster.

Terry
Boyd
Quote:
Originally Posted by tcassidy
Regular backups are the only solution in either case.
Doesn't sound like much of a solution unless you keep archival copies of every backup. If one file out of hundreds of thousands is corrupt, how long will it take before you notice the problem? And then, how many backups will you need to search through to find a usable copy of that file?
Ken in Regina
No argument from me re: regular backups.

But he makes a reasonable observation for scheduling frequency decisions. The article and report are in the context of huge volume use; Google servers in this case. The consequences of not scheduling often enough are obvious. The consequences of scheduling too frequently are higher operational costs, like power consumption, CPU time, extra backup storage media and space, etc. This information adds to their ability to make good scheduling decisions.

...ken...
tcassidy
Quote:
Originally Posted by Boyd
Doesn't sound like much of a solution unless you keep archival copies of every backup. If one file out of hundreds of thousands is corrupt, how long will it take before you notice the problem? And then, how many backups will you need to search through to find a usable copy of that file?
I hadn't thought of that. Maybe I will make sure the o/s drive is cloned and I don't keep ever changing data on it. I never liked the idea of documents, photos etc. on my o/s drive anyway.

Terry
Ken in Regina
Boyd,

The problem will appear the first time the file is accessed after the UBER reaches a point that the data is unusable. Either the user software or the backup process, whichever is first to access it, will discover the bad file when trying to read it. The immediately previous backup will most likely be good.

The way these processes are managed the recovery is usually a trivial matter and mostly automatic.

For example, the first line of backup in a commercial setting is often the use of RAID-type configurations in which the files are, in a sense, self-correcting on the fly.

...ken...
Ken in Regina
Terry, as we've discussed elsewhere, I'm pretty much at the point of having most of my data on a non-system drive.

I use XXClone to clone my system drive. The paid version has the ability to update the clone with only changed data so it encourages me to keep the clone current a little more frequently.

I'm still dithering between using Windows backup for the data drive versus the file compare/sync features of FreeCommander. So right now I do both. Not for everyone but since getting rid of all but two Windows systems I have hard drives to burn.

...ken...
Boyd
Quote:
Originally Posted by Ken in Regina
The problem will appear the first time the file is accessed after the UBER reaches a point that the data is unusable.
Ah, OK then that isn't so bad I guess.

My primary machine is a MacBook Air with a 512gb SSD, so I occasionally worry about data loss. But it has been rock solid for 3 years now. It is continuously backed up to a network drive with weekly backups to an external drive that I store offsite, and I make bootable clones and store them separately as well.

Apple has been selling SSD based laptops for awhile now, and aside from bad batches of drives, I don't read about very many problems. If there were serious data integrity problems, seems like you would read about them. But of course, as my laptop gets older, this is something I will probably worry about more.
Ken in Regina
Sounds like you've got it covered, Boyd.

Just to clarify, the article was not an alarmist article to scare people away from SSDs. It was to summarise a data analysis that has finally become available about *how* they fail. It seems clear their failure patterns are different. Not better or worse, overall; just different.

As the article points out, when it comes to complete drive failure SSDs may be more reliable than conventional hard drives. It also squashes the concerns about SSDs being vulnerable to failure from too many write cycles.

What it does observe is that SSDs are more susceptible to unrecoverable bit errors than conventional hard drives so mitigation for data loss needs to be looked at a little differently.

...ken...
Ken in Regina
For anyone interested here's a decent description of how SSDs work. Well, I found it interesting.

http://www.extremetech.com/extreme/210492-extremetech-explains-how-do-ssds-work?utm_source...ch+%28Extremetech%29

The site is terrible for ads but the article is probably worth a short time there.

...ken...
SpadesFlush
I just dropped two external drives on the floor at the same time. One was an old-style HD and the other was as SSD. The first one didn't survive and the second one did. So, reliability is one of those "it depends..." topics.


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