> If you had a 64G flash device which was rewriteable 2 million times > (which may be on the low end even, I can't find the rewrite spec for > the Intel SSD) you would have to write 64G*2,000,000 writes = 128 > petabytes. 128P/73T per year means this could last you for 1,753 years. > Is my math right? It's so easy to be off by an order of magnitude in
Sorry, but you're way off. Given the specs you mentioned, you would need to write 2Megabytes to blow the drive, if only you write a single byte 2,000,000 times in the same location. The key is: While you're doing writes, how well does your usage pattern distribute the writes across different blocks each time? If you are continually doing database operations, you might simply be writing and rewriting in tight clusters of disk blocks all the time... Be cautious. I can think of one way to possibly protect yourself from this sort of problem. I think (but I'm not totally sure - so please confirm with developers or experts) that ZFS uses copy-on-write algorithm for disk block allocation, which means the filesystem will choose to overwrite *different* blocks instead of overwriting the same block that was previously written. I think this would help distribute your writes throughout the physical medium, and alleviate at least some of the risk. _______________________________________________ Discuss mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
