On 2012-Aug-02 18:30:01 +0530, opensolarisisdeadlongliveopensolaris <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote: >Ok, so the point is, in some cases, somebody might want redundancy on >a device that has no redundancy. They're willing to pay for it by >halving their performance.
This isn't quite true - write performance will be at least halved (possibly worse due to additional seeking) but read performance could potentially improve (more copies means, on average, there should be less seeking to get a a copy than if there was only one copy). And non-IO performance is unaffected. > The only situation I'll acknowledge is >the laptop situation, and I'll say, present day very few people would >be willing to pay *that* much for this limited use-case redundancy. My guess is that, for most people, the overall performance impact would be minimal because disk write performance isn't the limiting factor for most laptop usage scenarios. >The solution that I as an IT person would recommend and deploy would >be to run without "copies" and instead cover you bum by doing backups. You need backups in any case but backups won't help you if you can't conveniently access them. Before giving a blanket recommendation, you need to consider how the person uses their laptop. Consider the following scenario: You're in the middle of a week-long business trip and your laptop develops a bad sector in an inconvenient spot. Do you: a) Let ZFS automagically repair the sector thanks to copies=2. b) Attempt to rebuild your laptop and restore from backups (left securely at home) via the dodgy hotel wifi. -- Peter Jeremy
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