On Thu, Oct 06, 2016 at 03:42:36AM +0100, Adam Richmond-Gordon wrote: > Thank you for pointing that out - I had it in my head that a single > log device would be safe.
There's only one failure mode (AFAIK) where a single log device will cause data loss; if your box crashes or has an unclean shutdown (say due to a power failure) while there are uncommitted entries on the log device, and the device fails before the system comes back online to process them. If the device dies while the system is running the log will fall back to being on the pool and any uncommitted entries are still in memory and won't be lost. If the device dies after a clean shutdown or poweroff there won't be any uncommitted entries on it and when the system comes up it will fail the device and again just fall back to an on-pool log. So while it's true that a single log device is non-redundant, it's a lot less "not safe" than say a non-redundant pool. You'd have to be pretty unlucky to actually have data loss from losing a non-redundant log device. Of course, depending on the importance of your data, that might not be a risk you want to take. But for a budget sensitive system, a single high-cost SSD for a log isn't an insane configuration if you think the odds of your system crashing/powering off dirty at the exact same time your log device dies are pretty low. ------------------------------------------- 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
