On Fri, Jun 14, 2013 at 7:11 PM, Todd And Margo Chester
<[log in to unmask]> wrote:
> On 06/10/2013 07:06 PM, jdow wrote:
>>
>> Just a little note, Vladimir, please be aware that there appears to be
>> a problem with SSDs when you read the same portion of the disk very many
>> times per day. The section of flash seems to lose data and cannot be
>> refreshed after a couple years. We have customers who use SSDs in theme
>> park rides in the vehicles for an audio server. It was a short, ride
>> length, audio track repeated every run for the ride vehicle - every few
>> minutes for a 12 hour day 365 days per year.
>
>
> Hi Jdow,
>
> Just an observation.  This problem occurs on non-linux machines
> only?  I could be wrong now, but doesn't Linux cache everything
> you read from your hard drive, so you really only read from
> the drive once?  Everything opens 4 times faster on my machine
> the "second" time I open it.  This would make the multiple read
> problem not such a problem, unless the data is constantly
> changing?

Linux uses the RAM not in use by active processes as disk cache. All
modern operating systems use disk cache, and there are a stack of
performance reasons to do so. But it eventually has to get written to
disk, and this is an ongoing, low priority task done constantly by the
kernel, or you'd not be able to rely on your log files or file system
to be consistent after a reboot or a system crash.

Some data does change constantly: "atime" on default configured
filesystems, for example, is writing to the directory information for
every file you even read from, and it's a nasty waste of write cycles
for SSD.