Status of SSDs under Fedora ?
pmeyer at themeyerfarm.com
Thu Jun 10 22:19:13 UTC 2010
On 06/10/2010 03:56 PM, Linuxguy123 wrote:
> On Thu, 2010-06-10 at 14:50 -0700, Konstantin Svist wrote:
>> On 06/10/2010 01:53 PM, Linuxguy123 wrote:
>>> I'm thinking of getting an Intel 160 GB SSD. How would it work under
>>> Linux ?
>>> I'm using ext4 for that drive right now. Is there a better filesystem
>>> for SSDs ?
>>> Is there anything that I should be aware of as far as switching ?
> Have you run an SSD ? Is longevity really an issue or is it folklore ?
It is bot real and folklore! :)
The fact is that any SSD, or other NAND type device has a limited number
of writes per address. The real question is:
"With your data needs and patterns, will you actually need to write to
the same address over 100,000 times?"
For most people, that is a big fat NO. The drives are smart enough to
re-arrange data around failed memory addresses. So what happens most
often is a very slight decrease in available space over time.
The advice given is just smart, because most file systems will update
the same physical disk 'block' containing inode data whenever a file is
accessed (atime). The chances of that update hitting the exact address
every time is quite high.
So, theoretically, if you just read a file on an SSD 100,000 times you
could destroy a single address location on the SSD. The device will map
around it, thus simply dropping available space by one address. For
most applications that is no big deal, but for some things that will add
up very quickly.
So yes, you lose data over time, and you can avoid some of that with
obvious measures as explained.
So no, with drives in the GB range, who really cares? Almost no-one.
When NAND devices were well under 1GB, then yes, it could matter quite a
Not all drives are specifically NAND based, but even the newer
technologies have a limit on how many times an address can be written
to, so the principle is the same.
Do you need atimes to be correct for you specific applications? If not,
then why not turn them off?
The same is true of the other issues mentioned.
Personally, I have used 2 and 4 GB NAND (the worst type) drives on
embedded systems for several years (some since 2005). No attempt was
made to alter atimes or any thing else. They are still running, and
still have lots of free space! :)
Your smart phone does the same thing. :)
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