immediate write to disk

immediate write to disk

Post by Doug Gw » Tue, 30 Jan 1990 08:11:49

>I would like to find out how portable (robust) the immediate to disk
>system call is across the various architectures or ports of UNIX(r).
>I beleive the system call that causes immediate writes is o_sync (???).
>Can anyone elaborate on this. It would certainly have an impact on
>database engine development requesting a commit.

I think you must be referring to an O_SYNC flag to the open()/fcntl()
system calls.  It is not universally available in UNIX implementations;
however, it is documented as a standard part of UNIX System V Release
3.2 and therefore should be supported in all subsequent releases of
UNIX System V.

1. ext3 fs: no userspace writes == no disk writes ?

Hi all,

I have a question about ext3 write activity.

I am considering using an ext3 fs on a CompactFlash disk for my
data-logging application (power can disapear anytime).
The quantity & frequency of the data logged itself is not a
problem at all considering flash wear.

But I'm a bit worried about the kernel/ext3 doing regular writes
by itself even when there are no userspace writes.  (worries are
partially caused by memories from long time ago about idle laptop
doing regular writes on disk).

Anybody out there who knows how this works ?

Can I use an ext3 fs without having regular "automatic" writes to
the device it is located on ?  (and thus not destroy my CompactFlash
devices !)

        Rob van Nieuwkerk

PS1: of course nothing from userspace should write frequently to
    the fs, and if there is regular read-activity the fs should
    be mounted with "noatime")

PS2: yes, I know that jffs exists
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