[zfs-discuss] ZFS and Power Loss

nick pitlosh via zfs-discuss zfs-discuss at list.zfsonlinux.org
Tue May 5 12:44:16 EDT 2015


whats the zil on?

On Tue, May 5, 2015 at 12:43 PM, nick pitlosh <nickpitlosh at gmail.com> wrote:

> tru dat.
>
> On Tue, May 5, 2015 at 11:48 AM, Gordan Bobic via zfs-discuss <
> zfs-discuss at list.zfsonlinux.org> wrote:
>
>> I think the original point was that your SSD may not be as reliably in
>> the power loss scenario as you think. Try disabling write caching on your
>> ZIL SSD, set sync=always and test the application with O_SYNC. It is
>> plausible that disabling write cache on the ZIL SSD may make the problem go
>> away.
>>
>>
>> On Tue, May 5, 2015 at 4:44 PM, Dan Swartzendruber via zfs-discuss <
>> zfs-discuss at list.zfsonlinux.org> wrote:
>>
>>> On 2015-05-05 11:40, Uncle Stoat via zfs-discuss wrote:
>>>
>>>> On 05/05/15 16:04, Adam Boyhan wrote:
>>>>
>>>>> That was what I was thinking.  However, I still run into issues even
>>>>> when running sync=always.
>>>>>
>>>>
>>>> If you're losing data, then the problem is likely to be outside of ZFS,
>>>> or your SSD isn't fast enough.
>>>>
>>>
>>> Maybe I am confused, but this doesn't sound right to me.  I thought if
>>> you were O_SYNC, the contract was that the kernel would not return until
>>> the write had committed to stable storage.  If using an SLOG, the client is
>>> told the write completed even though it's only in SLOG still.  If you power
>>> fail while that happens, on reboot, when the pool is imported, anything in
>>> the SLOG should be getting replayed and committed to spinning rust.  Or am
>>> I missing something?
>>>
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>>
>>
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>
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