> On Jan 23, 2017, at 9:54 AM, Gernot Straßer <[email protected]>
> wrote:
>
> Hi Robert,
>
> so let me try the other way around then: Do you know a device where the
> manufacturer explicitly says so?
STEC did. They also said synchronize_cache is a nop.
I’ve been working a lot with similar Toshibas recently. In general, nice drive
and I don’t
notice any significant impact for enabling or disabling synchronize_cache — a
good thing.
— richard
>
> 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
>>>>
>>>
>>>
>>
>>
>
>
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