Hi Robert, so let me try the other way around then: Do you know a device where the manufacturer explicitly says so?
Regards Gernot -----Ursprüngliche Nachricht----- Von: Robert Mustacchi [mailto:[email protected]] Gesendet: Montag, 23. Januar 2017 18:45 An: [email protected] Betreff: Re: AW: [smartos-discuss] smartos ssd disk question On 1/23/17 9:36 , Gernot Straßer wrote: > Most (if not all) so called of enterprise class SSD claim to be power-save > (being equipped with supercaps to power the drive until DRAM write cache is > emptied). > In case of a power failure no system will be able to send a synchronize > command to the drive, so what sense would the supercap make if that was a > requirement? > Does anybody have a suggestion on how to test that (besides pulling the power > cable)? Hi Gernot, I think you're looking at this from the wrong perspective. For example, ZFS will not treat the write as stable until it receives a synchronize cache command. For some devices it may be that the synchronize cache command is required to get outstanding writes into the state that it will be protected by the supercap. Obviously, this is something that's going to vary from drive to drive. If it's totally fine for these Toshiba's great. If someone wanted to make a chance to illumos that said synchronize cache was unnecessary on those devices, then I'd want the manufacturer to explicitly say so. Robert > -----Ursprüngliche Nachricht----- > Von: Robert Mustacchi [mailto:[email protected]] > Gesendet: Montag, 23. Januar 2017 18:30 > An: [email protected] > Betreff: Re: [smartos-discuss] smartos ssd disk question > > On 1/23/17 9:20 , Youzhong Yang wrote: >> it is power safe and we've tested it here. >> >> https://toshiba.semicon-storage.com/us/product/storage-products/enter >> p >> rise-ssd/px02smb-px02smfxxx.html?sug=1 > > Sure, it does say it's power safe. Are you sure that means you don't need to > issue synchronize cache commands to the device? For some devices, you still > need to issue synchronize cache commands even if they're power safe. If it > works, great. Hopefully that just means synchronize cache commands are a > no-op. > > Robert > >> On Mon, Jan 23, 2017 at 12:01 PM, Robert Mustacchi <[email protected]> wrote: >> >>> On 1/23/17 6:29 , Youzhong Yang wrote: >>>> Add something like this to /kernel/drv/sd.conf: >>>> >>>> "TOSHIBA PX02SMF020 ", "cache-nonvolatile:true", >>>> >>>> I don't think the sd.conf comes with smartos image has it, so you >>>> need to build your own image. >>> >>> In general, you should _never_ set this value. You have basically >>> told the system that this device is power safe and never requires a >>> synchronize cache command. This is not true for most devices and a >>> poorly timed panic will result in data loss on the one device whose >>> purpose is to protect its data: the slog. >>> >>> Note, when I generally talk about an SSD being power safe, that does >>> not mean that this can be set to true. The devices generally only >>> guarantee that data is safe after a synchronize cache command. >>> >>> I don't have as much experience with these Toshiba drives, so it may >>> be that their datasheet tells you something else in this case. >>> >>> 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
