On 07/08/2016 07:44 AM, vincent wrote: > > > Op 7/8/2016 om 12:23 PM schreef Jean-David Beyer: >> Why all this concern about how long a disk (or SSD) drive can stay up >> after a power failure? >> >> It seems to me that anyone interested in maintaining an important >> database would have suitable backup power on their entire systems, >> including the disk drives, so they could coast over any power loss. >> > As others have mentioned; *any* link in the power line can fail, from > the building's power > to the plug literaly falling out of the harddisk itself. Using multiple > power sources, > UPS, BBU etc reduce the risk, but the internal capacitors of an SSD are > the only thing > that will *always* provide power to the disk, no matter what caused the > power to fail. > > It's like having a small UPS in the disk itself, with near-zero chance > of failure. > > Thank you for all the responses. The only time I had a power supply fail in a computer was in a 10 year old computer. When storm Sandy came by, the power went out and the computer had plenty of time to do a controlled shutdown. But when the power was restored about a week later, the power flipped on and off at just the right rate to fry the power supply, before the system even started up enough to shut down again. So I lost no data. All I had to do is buy a new computer and restore from the backup tape. Of course, those capacitors in the disk itself could fail. Fortunately, there have been giant improvements in capacitor manufacture reliability since I had to study reliability of large electronic systems for a military contract way back then. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key:166D840A 0C610C8B Registered Machine 1935521. /( )\ Shrewsbury, New Jersey http://linuxcounter.net ^^-^^ 10:50:01 up 36 days, 16:52, 2 users, load average: 4.95, 5.23, 5.18 -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
