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Re: Tracing Filesystem Accesses



Paul E Condon wrote:
On 20110513_065059, Stan Hoeppner wrote:
On 5/13/2011 2:38 AM, Doug wrote:

According to some information on the various lists, you should *not* run
swap on
a SSD, because the SSD has a limited number of read/write cycles, and
swap uses
them up way too quickly.
That's pure FUD.  Read the following soup to nuts:
http://www.storagesearch.com/ssdmyths-endurance.html

You've read *speculation*.  There are hundreds of thousands of folks
around the globe using SSDs right now in their workstations for OS +
swap, and in high concurrent write load servers, mainly mail spools.  A
busy mail spool has a higher localized write load than swap.  In either
case I've yet to read of an SSD failing due to worn out cells.

I replaced a failed 4 year old Seagate Barracuda 120GB in my WinXP
workstation less than a month ago with a 32GB Corsair Nova SSD:
http://www.corsair.com/cssd-v32gb2-brkt.html

It was the cheapest ~30GB available at the time, $65 USD at Newegg, on
sale ($79 now).  I partitioned 15GB for XP + aps + swap file, saving the
other 15GB, maybe for a Squeeze desktop install.  Ping me in 5 years and
I'll let you know if this SSD has failed due to worn out cells. ;)
...snip

Stan,
I'm sure there can be progress in any technology, but it is surely
true that there was once-upon-a-time, a re-write problem in the
underlying chip technology that goes into today's SSDs. I tend to use
cast off older stuff in my home computing. When, in the past, would
you say that the SSD technology became reliable? It sort of puts a
cutoff on just how old I should put up with. Or did the technology
problems get solved before anything called SSD get offered on the
comsumer market?

And, the rewrite story for thumb drives ( I think that is what the
small, fit in your pocket USB devices are called. ) is the story also
FUD, or do they use a different, inferior technology?

Before we go any further, lets get a couple of things sorted out. What type of SSD (Solid State Drive) are you all talking about here?

If it contains Flash memory, then yes, there is a limit to the number of ERASE cycles each sector can do. How long they last depends on a number of factors, not the least of which is how old the chips are. The first generations of flash memory chips could only be erased about 10,000 times before they started to fail. This could be mitigated by decent firmware that did load leveling behind the scenes. But there was still a finite limit to how long they could be used before they wouldn't erase anymore. Newer chips can handle 100,000-250,000 erase cycles. So decent drivers can help them last for several years even under heavy use. If the wear is spread out over a large space, it almost appears to last forever. But I still wouldn't want to use them for files that were frequently replaced or rewritten. I still think of them as Read-Mostly memory components.

Bob McConnell
N2SPP


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