delaylog in mount options

[Charlie Nugent]

Hi

During our OEM installation of SLES 11 SP3 we're mounting internal disks with the following options in /etc/fstab:

rw,noatime,nodiratime,attr2,noquota,allocsize=4m,inode64,nobarrier

However, a mount command will produce:

/dev/sdb2 on /data1 type xfs (rw,noatime,nodiratime,attr2,delaylog,nobarrier,inode64,allocsize=4096k,noquota)

We have not included the delaylog option.  How was this added, what effect does it have and how can we remove it?

rgds, Charlie

[Marcus Schäfer]

Hi,

> However, a mount command will produce:
> /dev/sdb2 on /data1 type xfs
> (rw,noatime,nodiratime,attr2,delaylog,nobarrier,inode64,allocsize=4096k
> ,noquota)
> We have not included the delaylog option. How was this added, what
> effect does it have and how can we remove it?
> rgds, Charlie

I'm not an xfs expert but what I know from delaylog is that the entry
to the journal is hold in memory as long as possible before it's actually
written. Thus it's a performance option and as far as I know it's the
default when you just mount an xfs.

I don't know whether it's a compiled in option or if the default mount
behavior can be influenced by a config file. All I know for sure is
that kiwi does not handle this explicitly :)

Regards,
Marcus
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[Charlie Nugent]

Hi Marcus

thanks for your response

We're concerned that "delaylog" mount option may adversely affect our systems.  Is there someone in SUSE who
you could recommend as an XFS expert?

thanks, Charlie

[Marcus Schäfer]

Hi,

> We're concerned that "delaylog" mount option may adversely affect our
> systems. Is there someone in SUSE who
> you could recommend as an XFS expert?

Hmm, I don't know a direct candidate but Robert(here on the list) uses XFS,
I'm sure he know a bit about it and if not he might know more people
around XFS

Regards,
Marcus
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[Robert Schweikert]

On 02/07/2014 12:47 PM, Marcus Schäfer wrote:
> Hi,
>
>> We're concerned that "delaylog" mount option may adversely affect our
>> systems. Is there someone in SUSE who
>> you could recommend as an XFS expert?
>
> Hmm, I don't know a direct candidate but Robert(here on the list) uses XFS,
> I'm sure he know a bit about it and if not he might know more people
> around XFS

yup, I do not know why delaylog would show up. Following up with the
filesystem experts.

Will respond when I have more details.

Later,
Robert

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Robert Schweikert MAY THE SOURCE BE WITH YOU
SUSE-IBM Software Integration Center LINUX
Tech Lead
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rsch...@ca.ibm.com
781-464-8147

[Charlie Nugent]

Hi Robert,

thanks for your help.  Looking forward to your response

rgds, Charlie

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rgds, Charlie Nugent

[Robert Schweikert]

Hi,

Heard back from one of our filesystem experts, I will paraphrase.

On 02/10/2014 12:27 PM, Charlie Nugent wrote:
> Hi Robert,
>
> thanks for your help. Looking forward to your response

delaylog is a default mount option and thus it shows up in mount options
even if you did not set it. It can be disabled with "nodelaylog" (no
quotes.)

It does have performance implications but they should be entirely
positive ones. Delayed logging saves some space in the journal and thus IO.

HTH,

Robert

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[Charlie Nugent]

Excellent news, thanks very much folks

We intend to run tests to evaluate on our systems and the ability to disable 
delaylog may come in handy

thanks again, Charlie

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rgds, Charlie Nugent