On 1/19/15 17:04 , Greg Treantos via smartos-discuss wrote: > Is there a mixed message from the SmartOS team. On one hand SmartOS is > pushed as a stateless platform thus the exclusion of UPS monitoring. > Reading this thread it seems like the answer hey if you want performance > you need to spend big bucks on a battery backup log device.I don't get it.
I don't know, perhaps we just focus on different things that are important? At the end of the day, servers will panic, have power outages, or have something go wrong and therefore you should handle that and plan it. A UPS doesn't really do much for you in the OS panics. You have to plan for having a hard power loss event or a hard loss of service, that's why we at Joyent don't particularly care about it. Just because we don't care about something doesn't mean someone else can't come around and care. We made the design choice to say that KVM always does synchronous writes. That was so we didn't have to worry about guests properly issuing cache flushes or enabling barriers in Linux parlance, etc. A common solution to the issue of having a high synchronous write workload is a slog. It's something that we pioneered at Fishworks as part of building a storage appliance. Importantly, you do need a *power-safe* device. But that doesn't have to be a device that has a physical battery in it. In fact, a bunch of the super-cap based flash drives were designed that way because of the fishworks project. Now you might ask, given what we believe about a server, why does this matter? The point is that if we say that we've written your data and acknowledged it, whether you've done that by doing a synchronous write or calling fsync(2), if we return you and have not actually guaranteed your data is on stable storage, then we have failed in our promises. Does that clarify what you're seeing as mixed messages? Robert ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
