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Re: Disable read and write caches in HFS+ filesystem.
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Re: Disable read and write caches in HFS+ filesystem.


  • Subject: Re: Disable read and write caches in HFS+ filesystem.
  • From: Irad K <email@hidden>
  • Date: Mon, 30 Apr 2018 15:54:14 +0300

Just a small update, I understand from HFS+ spec that I can simply create a
RAM disk and this bit will probably be set automatically.

If that's the case, then the solution is to create a RAM disk and copy the
contents to it bypassing the cache.

However, I'd prefer to be based on .dmg based filesystem. is it possible ?

thanks,

Irad

On Mon, Apr 30, 2018 at 2:17 PM, Irad K <email@hidden> wrote:

> I've created empty HFS+ filesystem represented by dmg image file. For
> security reasons I'd like to make sure every IO applies directly to the dmg
> file and not through any kind of memory in the middle.
>
> Is there any way to cancel the option for read and write caching while
> mounting the filesystem?
>
> During my research about this theme, I've discovered that HFS+ header
> contain attributes field, and one of its containing bits in volume
> attributes field named kHFSVolumeNoCacheRequiredBit. It set if we want
> that blocks from this volume wouldn't not be cached, which is pretty much
> what I need. However, i don't have a clue about how to set it on.
>
> Any idea how to configure this volume properly (command-line, application,
> API, etc .. ) ?
>
> thanks,
>
> Irad
>
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References: 
 >Disable read and write caches in HFS+ filesystem. (From: Irad K <email@hidden>)

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