[Pharo-project] Design change possible with fast SSD's possible?

Janko Mivšek janko.mivsek at eranova.si
Tue Jan 17 21:48:29 CET 2012


.. also SSD won't necessary use Flash technology in the future, there
are already alternatives close to production level, which solve exactly
that write problem. In any case, in few years we will have such a
hierarchical persistent memory from slow SSD up to fastest CPU caches
available.

S, Michael Haupt piše:
> ... BTW that's what I meant with optimisations.
> 
> Am 14.01.2012 um 19:34 schrieb Guido Stepken <gstepken at googlemail.com
> <mailto:gstepken at googlemail.com>>:
> 
>> Read about "wear leveling"? So, no problem with write cycles. For
>> example yffs2 filesystem gives you a tremendous gain in lifetime of
>> your USB flash storage.
>>
>> regards, Guido Stepken
>>
>> Am 14.01.2012 15:56 schrieb "Michael Haupt" <mhaupt at gmail.com
>> <mailto:mhaupt at gmail.com>>:
>>
>>     Hi,
>>
>>     2012/1/14 Janko Mivšek <janko.mivsek at eranova.si
>>     <mailto:janko.mivsek at eranova.si>>:
>>     > Conclusion? Why RAM won't be just a L3 cache in a whole hiearchy of
>>     > caching from SSD up to CPU? Automatic, supported by OS or even
>>     hardware,
>>     > as CPU caches are? Then image wont be needed to be read to RAM and
>>     > snapshoted back to disk, it can be run directly from disk.
>>
>>     SSDs are Flash memory. The number of write cycles is limited before
>>     the memory starts to fail. Smalltalk frequently performs GC, which
>>     involves moving objects, i.e., writing. Writing is also much slower
>>     than reading, and AFAIK possible only block-wise (with a block being
>>     significantly larger than your average object). Flash file systems
>>     apply optimisations to distribute writing evenly, avoiding excessive
>>     writing in some places and consequent earlier failure.
>>
>>     Best,
>>
>>     Michael
>>

-- 
Janko Mivšek
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