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 _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
