On 3/13/2013 2:23 PM, Steve Crawford wrote: > On 03/13/2013 09:15 AM, John Lister wrote: >> On 13/03/2013 15:50, Greg Jaskiewicz wrote: >>> SSDs have much shorter life then spinning drives, so what do you do >>> when one inevitably fails in your system ? >> Define much shorter? I accept they have a limited no of writes, but >> that depends on load. You can actively monitor the drives "health" >> level... > > What concerns me more than wear is this: > > InfoWorld Article: > http://www.infoworld.com/t/solid-state-drives/test-your-ssds-or-risk-massive-data-loss-researchers-warn-213715 > > > Referenced research paper: > https://www.usenix.org/conference/fast13/understanding-robustness-ssds-under-power-fault > > > Kind of messes with the "D" in ACID. > > Cheers, > Steve
One potential way around this is to run ZFS as the underlying filesystem and use the SSDs as cache drives. If they lose data due to a power problem it is non-destructive. Short of that you cannot use a SSD on a machine where silent corruption is unacceptable UNLESS you know it has a supercap or similar IN THE DISK that guarantees that on-drive cache can be flushed in the event of a power failure. A battery-backed controller cache DOES NOTHING to alleviate this risk. If you violate this rule and the power goes off you must EXPECT silent and possibly-catastrophic data corruption. Only a few (and they're expensive!) SSD drives have said protection. If yours does not the only SAFE option is as I described up above using them as ZFS cache devices. -- -- Karl Denninger /The Market Ticker ®/ <http://market-ticker.org> Cuda Systems LLC
