On Wed, Jun 11, 2008 at 4:31 AM, Adam Leventhal <[EMAIL PROTECTED]> wrote:
> On Jun 11, 2008, at 1:16 AM, Al Hopper wrote:
>>
>> But... if you look
>> broadly at the current SSD product offerings, you see: a) lower than
>> expected performance - particularly in regard to write IOPS (I/O Ops
>> per Second)
>
> True. Flash is quite asymmetric in its performance characteristics.
> That said, the L2ARC has been specially designed to play well with the
> natural strengths and weaknesses of flash.
>
>> and b) warranty periods that are typically 1 year - with
>> the (currently rare) exception of products that are offered with a 5
>> year warranty.
>
> You'll see a new class of SSDs -- eSSDs -- designed for the enterprise
> with longer warranties and more write/erase cycles. Further, ZFS will
> do its part by not killing the write/erase cycles of the L2ARC by
> constantly streaming as fast as possible. You should see lifetimes in
> the 3-5 year range on typical flash.
>
>> Obviously, for SSD products to live up to the current marketing hype,
>> they need to deliver superior performance and *reliability*.
>> Everyone I know *wants* one or more SSD devices - but they also have
>> the expectation that those devices will come with a warranty at least
>> equivalent to current hard disk drives (3 or 5 years).
>
> I don't disagree entirely, but as a cache device flash actually can be
> fairly unreliable and we'll pick it up in ZFS.
>
>> So ... I'm interested in learning from anyone on this list, and, in
>> particular, from Team ZFS, what the reality is regarding SSD
>> reliability. Obviously Sun employees are not going to compromise
>> their employment and divulge upcoming product specific data - but
>> there must be *some* data (white papers etc) in the public domain that
>> would provide some relevant technical data??
>
>
> A typical high-end SSD can sustain 100k write/erase cycles so you can
> do some simple math to see that a 128GB device written to at a rate of
> 150M/s will last nearly 3 years. Again, note that unreliable devices
> will result in a performance degradation when you fail a checksum in
> the L2ARC, but the data will still be valid out of the main storage
> pool.
>
> You're going to see much more on this in the next few months. I made a
> post to my blog that probably won't answer your questions directly, but
> may help inform you about what we have in mind.
>
> http://blogs.sun.com/ahl/entry/flash_hybrid_pools_and_future
>
> Adam
>
> --
> Adam Leventhal, Fishworks http://blogs.sun.com/ahl
>
>
Ahh Haa! So this is the "secret" project (probably one of many) that
you guys have been working on! :) Great post and I really
appreciate how this thread has provided lots of interesting stuff to
think about.
I think that I'll (personally) avoid the initial rush-to-market
comsumer level products by vendors with no track record of high tech
software development - let alone those who probably can't afford the
PhD level talent it takes to get the "wear leveling" algorithms
correct - and then to implement them correctly. Instead I'll wait for
a Sun product - from a company with a track record of proven design
and *implementation* for enterprise level products (software and
hardware).
Otherwise, I think that I would be really upset with an SSD device
that died every 2+ years - even if it has a 5 year warranty. No one I
know would tolerate that kind of system disruption from todays hard
disk drives - despite anticipated failures. Its more aggravation
that most production oriented systems can simply live without!
Again - thanks to all contributors for this interesting thread.
Regards,
--
Al Hopper Logical Approach Inc,Plano,TX [EMAIL PROTECTED]
Voice: 972.379.2133 Timezone: US CDT
OpenSolaris Governing Board (OGB) Member - Apr 2005 to Mar 2007
http://www.opensolaris.org/os/community/ogb/ogb_2005-2007/
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