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Re: Is disabling doublewrite safe on ZFS?


On 17/08/2018 09:20, Gionatan Danti wrote:
On 16/08/2018 23:41, Vladislav Vaintroub wrote:
I  think it is up to the OS kernel  how to handle interrupt request when a system call is in progress. If kernel reacts to signals/exceptions by interrupting write() call in the middle of copying data from your buffer to the page cache, nothing would help.  And what means “in the middle”, is also unclear. There would be some kind of granularity (page size in pagecache maybe). I do not know what different kernels do in such cases, but this the is level where ZFS is not involved at all.

Well, the manual [1] seems quite explicit about the possibility to have write() interrupted by a signal (and, by extension, due to a process crash):

"If a write() is interrupted by a signal handler before any bytes are written, then the call fails with the error EINTR; if it is interrupted after at least one byte has been written, the call succeeds, and returns the number of bytes written."

With such a premise, do you think disabling doublewrite still be safe?

[1] https://linux.die.net/man/2/write

Hi all,
anyone with some suggestion/insight on the matter?


Danti Gionatan
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