[CentOS] write barrier support in CentOS 6

Tue Apr 1 22:00:18 UTC 2014
Tom Robinson <tom.robinson at motec.com.au>

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 at 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?
> Take a look here:
> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/writebarrieronoff.html
>
> Regards,
> Lec
Thanks Lec, I did read this already. It does address filesystems but not LVM. Are write barriers
enabled for LVM? Write barriers need to be implemented through the entire stack for them to work. If
you have ext4 on LVM on MD not having them on LVM would break the chain.  N'est-ce pas?

>> I believe you can look through the RHEL tech notes.  Here they are for
>> 6.5:
>>
>> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.5_Technical_Notes/index.html
>>
>> If you require barriers, you can always use the mainline kernel from
>> elrepo.  You can read about the mainline and long-term packages here:
>>
>> http://elrepo.org/tiki/kernel-lt
>>
>> You probably want the kernel-ml packages, but that page doesn't mention
>> the -lt packages.  Lots of CentOS admins use these kernels (including
>> me) and are happy with them.
>>
>> --keith
>>
>

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