Re: raw aio write guarantee

[<iodophlymiaelo@gmail.com>]

On 9/28/05, Valdis.Kletnieks@vt.edu <Valdis.Kletnieks@vt.edu> wrote:
> On Wed, 28 Sep 2005 00:12:33 PDT, iodophlymiaelo@gmail.com said:
>
> > Just a quick question: How can a user-mode application ensure that an
> > AIO write on a raw block device (i.e. open()ed with O_DIRECT) has
> > really -really- been written to the disk and not residing in an on-disk
> > write cache where it could be lost in case of a power failure?
>
> Step 1: Make sure you buy disk drives that don't lie through their teeth
> regarding details such as "is the write cache enabled?" or "did the flush
> cache work?".  Such hardware can generate vast amounts of bad karma....
>
> Step 2: Buy a UPS.  A good one.  You can't lose the cache during a power failure
> that doesn't actually hit.
>
> Step 3: http://catb.org/~esr/jargon/html/M/molly-guard.html - You want these.
> Lots of them.
>

I was asking what a user-application can do to prevent data loss, not
an application-user.