Re: raw aio write guarantee

[Valdis . Kletnieks]

On Wed, 28 Sep 2005 00:12:33 PDT, iodophlymiaelo@xxxxxxxxx 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.

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