Re:A straight talk about btrfs
by pas on Thursday August 24, 2017 @05:47PM
(#15094337)
A hot spare is expensive. I want pure redundancy. That is making a one drive failure into a still perfectly operational server/node/box.
That's what RAID1 usually means.
And sure, you can't survive the next without replacing the failed drive and resyncing.
But the remount read only thing is something different. It's a useful failure mode, but doesn't help with operational simplicity.
(If the SATA cable is loose, the it'll cause intermittent failures, you'll see it in the log, and there will be a lot of resync events. And probably degraded performance, a lot of ATA (or SCSI errors in case of SAS), and other bus/command errors that go away on retry. And with SMART it's possible to at least guess that it's not the drive. It'd be great to have an error notification interface from the kernel and a tool could try to dig into the relevant subsystem's perf and health data to try to guess what's the faulty component exactly.)
That's what RAID1 usually means.
And sure, you can't survive the next without replacing the failed drive and resyncing.
But the remount read only thing is something different. It's a useful failure mode, but doesn't help with operational simplicity.
(If the SATA cable is loose, the it'll cause intermittent failures, you'll see it in the log, and there will be a lot of resync events. And probably degraded performance, a lot of ATA (or SCSI errors in case of SAS), and other bus/command errors that go away on retry. And with SMART it's possible to at least guess that it's not the drive. It'd be great to have an error notification interface from the kernel and a tool could try to dig into the relevant subsystem's perf and health data to try to guess what's the faulty component exactly.)