Re: [lustre-discuss] Lustre [2.8.0] flock Functionality

[Martin Hecht]

Hello,

we use the flock mount option on all our lustre systems (currently some
2.5 versions) and are not aware of any issues due to that.

If your applications run on a single node (or require  locks only
locally) you could also try localflock.
localflock has less performance impact than the global flock. How much
impact you have depends on how heavily the applications make use of
locks. We have measured a few per cent on lustre 1.8 in simple tests,
but I think that the performance impact nowadays is even less, but as I
said, it depends on the IO pattern.

localflock is more risky than flock, because it makes your application
think that locks are there, but in fact they are not globally visible,
which may lead to strange effects with parallel applications spanning
several nodes. We were running localflock on one of our systems for some
time and occasionally heard about such problems from a few users.

best regards, Martin

On 03/28/2017 07:49 PM, DeWitt, Chad wrote:
> Good afternoon, All.
>
> We've encountered several programs that require flock, so we are now
> investigating enabling flock functionality.  However, the Lustre manual
> includes a passage in regards to flocks which gives us pause:
>
> "Warning
> This mode affects the performance of the file being flocked and may affect
> stability, depending on the Lustre version used.  Consider using a newer
> Lustre version which is more stable. If the consistent mode is enabled and
> no applications are using flock, then it has no effect."
>
> We are running Lustre 2.8.0 (servers and clients).  I've looked through
> Jira, but didn't see anything that looked like a showstopper.
>
> Just curious if anyone has enabled flocks and encountered issues?  Anything
> in particular to look out for?
>
> Thank you in advance,
> Chad
>
> 
>
> Chad DeWitt, CISSP | HPC Storage Administrator
>
> UNC Charlotte *| *ITS – University Research Computing
>
> 
>




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Re: [lustre-discuss] Lustre [2.8.0] flock Functionality

[Torsten Harenberg]

Am 28.03.17 um 21:43 schrieb Mohr Jr, Richard Frank (Rick Mohr):
> 
>> On Mar 28, 2017, at 1:49 PM, DeWitt, Chad  wrote:
>>
>> We've encountered several programs that require flock, so we are now 
>> investigating enabling flock functionality.  However, the Lustre manual 
>> includes a passage in regards to flocks which gives us pause:
>>
>> "Warning
>> This mode affects the performance of the file being flocked and may affect 
>> stability, depending on the Lustre version used.  Consider using a newer 
>> Lustre version which is more stable. If the consistent mode is enabled and 
>> no applications are using flock, then it has no effect."
>>
>> We are running Lustre 2.8.0 (servers and clients).  I've looked through 
>> Jira, but didn't see anything that looked like a showstopper.  
>>
>> Just curious if anyone has enabled flocks and encountered issues?  Anything 
>> in particular to look out for?
> 
> I have enabled flock on all my Lustre file systems (2.4.3 and 2.8), and I 
> have not yet encountered any issues.

running flock here as well on ~200 nodes with 2.5.3 servers and 2.8.0
clients without any problems.

Cheers

  Torsten

-- 
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
<>  <>
<> Dr. Torsten Harenberg torsten.harenb...@cern.ch  <>
<> Bergische Universitaet   <>
<> Fakutät 4 - PhysikTel.: +49 (0)202 439-3521  <>
<> Gaussstr. 20  Fax : +49 (0)202 439-2811  <>
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<><><><><><><>< Of course it runs NetBSD http://www.netbsd.org ><>
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Re: [lustre-discuss] Lustre [2.8.0] flock Functionality

[Mohr Jr, Richard Frank (Rick Mohr)]

> On Mar 28, 2017, at 1:49 PM, DeWitt, Chad  wrote:
> 
> We've encountered several programs that require flock, so we are now 
> investigating enabling flock functionality.  However, the Lustre manual 
> includes a passage in regards to flocks which gives us pause:
> 
> "Warning
> This mode affects the performance of the file being flocked and may affect 
> stability, depending on the Lustre version used.  Consider using a newer 
> Lustre version which is more stable. If the consistent mode is enabled and no 
> applications are using flock, then it has no effect."
> 
> We are running Lustre 2.8.0 (servers and clients).  I've looked through Jira, 
> but didn't see anything that looked like a showstopper.  
> 
> Just curious if anyone has enabled flocks and encountered issues?  Anything 
> in particular to look out for?

I have enabled flock on all my Lustre file systems (2.4.3 and 2.8), and I have 
not yet encountered any issues.

--
Rick Mohr
Senior HPC System Administrator
National Institute for Computational Sciences
http://www.nics.tennessee.edu

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[lustre-discuss] Lustre [2.8.0] flock Functionality

[DeWitt, Chad]

Good afternoon, All.

We've encountered several programs that require flock, so we are now
investigating enabling flock functionality.  However, the Lustre manual
includes a passage in regards to flocks which gives us pause:

"Warning
This mode affects the performance of the file being flocked and may affect
stability, depending on the Lustre version used.  Consider using a newer
Lustre version which is more stable. If the consistent mode is enabled and
no applications are using flock, then it has no effect."

We are running Lustre 2.8.0 (servers and clients).  I've looked through
Jira, but didn't see anything that looked like a showstopper.

Just curious if anyone has enabled flocks and encountered issues?  Anything
in particular to look out for?

Thank you in advance,
Chad



Chad DeWitt, CISSP | HPC Storage Administrator

UNC Charlotte *| *ITS – University Research Computing


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