If the takeover is administratively initiated then it's considered graceful and the cache is properly de-staged. If the takeover is due to a panic then the cache is not de-staged and will need to be rebuilt from scratch when the controller comes back online.
In both scenarios the surviving controller's extended cache becomes responsible for both controllers' workloads, so while in takeover mode the partner's FlashCache will load both its blocks and the partner's blocks into its cache. After the giveback is performed the partner's blocks that were being loaded into the surviving controller's cache will stale out and be ejected and replaced.
-----Original Message----- From: Eugene Vilensky [mailto:evilensky@gmail.com] Sent: Tuesday, December 13, 2011 6:49 PM To: Chris Muellner Cc: toasters@teaparty.net Subject: Re: flexcache and cold caches
Hi Chris,
How does this work for takeover situations? That is, to go from two flash caches to one...
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On Dec 13, 2011, at 6:42 PM, Chris Muellner chris@northlandusa.com wrote:
If OnTap 8.1+ is on your roadmap for upgrades then cold starts should become a thing of the past. Even today they should be few and far between and only due to power outages, upgrades, and hardware maintenance. Two of those can be planned and if you're incredibly lucky or fortunate you could possibly manage a graceful shutdown during a power event making all three a moot point.