On 11/18/2015 04:42 PM, John R Pierce wrote:
the /really/ hard one when rolling your own highly redundant systems
with high data integrity needed for things like transactional database
servers, is implementing redundant storage controllers with shared
writeback cache... you pretty much have to get into EMC class
hardware for this level of reliability with data integrity and
performance. and thats /really/ expensive stuff.
Yes it is, because it really is that hard to do shared writeback cache.
EMC, Nimble, NetApp, and the like cost what they do because of those HA
features. EMC storage processors have specialized shared backplanes and
replicated write caches just in case an SP goes down while the data to
be written is in cache and has yet to be committed (so that the
trespassing SP can write the correct data to disk). They also have
dedicated battery backup units and the whole concept of the 'vault'
drives to specifically save the write cache in a powerfail emergency.
But I would love to see something in the free software space that did
that kind of thing, with appropriate hardware.
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