HI Bob, > The ARC is a "hot" cache. The data might be updated a million times before > it is actually written to underlying store. If data is in the ARC, then it > is not read from the persistent store.
That’s what I was hoping, but I’m surprised by the “update a million times before it’s written” comment. Does the comment apply only to async-writes? Assuming async-writes are flushed every, e.g., 5 secs, would the “million updates" need to occur in that window? Once the ARC is warmed up, does the ARC-cached part of the filesystem then move at the speed of RAM (e.g., with the illusion of massive IOPS), regardless the underlying pool topology? So "mirror vs. raidz" and "SSD vs. HDD” decisions should be primarily focused on supporting the cache-miss and sync-writes cases? (excluding the "large-stream" case as such likely won’t cause ARC-evictions) K. ------------------------------------------ illumos: illumos-discuss Permalink: https://illumos.topicbox.com/groups/discuss/T4a93ce1686bc673e-M84501e8529e1326e16106b0d Delivery options: https://illumos.topicbox.com/groups/discuss/subscription
