[Nottingham] HDDs, SSDs, system speedups (Was: Nottingham Digest, Vol 300, Issue 8)

[Martin]

Camilo Mesias wrote:
> Hi,
> 
>> Note that the first generation of SSDs were crap. The present generation
>> look a bit better. The way to go is with a revamped SSD controller that
>> *transparently* implements RAID0/1/10 across multiple flash chips and
>> with intelligent wear levelling. A big plus will be gained when
>> filesystems also report to the SSD when sectors become free for reuse.
> 
> I'm not sure of the benefit of any RAID over flash chips within a
> device - if the chips themselves aren't individually replaceable. But

Higher read and write speed by using multiple chips in parallel. Also, 
the have the option of resilience if bits fail.

However... Could not the controller do a verify for every write and 
reallocate if a bit fails...?

> more intelligence between SSDs and filesystem would be good - aligning
> boundaries and freeing sectors (so the underlying flash can be
> pre-emptively erased for re-use). Also, if the SSD has to do some
> internal housekeeping at some point there may be ways of agreeing with
> the OS at which point it would be best to do it, to minimise impact.
> Finally - some SMART-like statistics so we can tell when a device is
> wearing out!

Good points, especially the SMART monitoring and checks.


So... Anything out there for that? And when?

Cheers,
Martin

-- 
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Martin Lomas
martin at ml1.co.uk
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