On 04/03/2014 06:25 AM, Tom Robinson wrote:
On 02/04/14 20:17, Alexandru Chiscan wrote:
On 04/02/2014 01:00 AM, Tom Robinson wrote:
On 01/04/14 17:49, Alexandru Chiscan wrote:
On 04/01/2014 06:27 AM, Keith Keller wrote:
On 2014-04-01, Tom Robinson tom.robinson@motec.com.au wrote:
Now, I understand that Red Hat (and therefore CentOS) backport many upstr= eam features into the stock kernel so how can I be sure that kernel 2.6.32-431.11.2.el6 has write bar= rier support?
from the kernel changelog (https://access.redhat.com/knowledge/sources/source_rpms/kernel-2.6.32-431.11...) the barrier support for filesystems, lvm (dm) and md is active from 2.6.32-82-el6
Thanks Alexandru,
I did look at the changelog but, for my untrained eye, I saw no specific reference to LVM there (and indeed still don't in your list above). Are you saying that because dm is patched, LVM is now implementing barriers correctly?
As what I know the LVM system is implemented on top of dm (device mapper) (see http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29) so it should handle the barrier requests if dm does it.
<quote> In the 2.6-series of the Linux Kernel, the *LVM is implemented in terms of the **device mapper http://en.wikipedia.org/wiki/Device_mapper*, a simple block-level scheme for creating virtual block devices and mapping their contents onto other block devices. This minimizes the amount of relatively hard-to-debug kernel code needed to implement the LVM. It also allows its I/O redirection services to be shared with other volume managers (such as EVMS http://en.wikipedia.org/wiki/Enterprise_Volume_Management_System). *Any LVM-specific code is pushed out into its user-space tools, which merely manipulate these mappings and reconstruct their state from on-disk metadata upon each invocation.* </quote>
Regards, Lec
Kind regards, Tom
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