[Novalug] remote caching auto-syncing file system?

James Ewing Cottrell, III jecottrell3@comcast.net
Fri Jun 12 14:48:03 EDT 2015


OK, so I put this up between a few servers at NIH...watched it synchronize...looked pretty slick.

UNTIL one day when what was Cached did not match what was Remote. I think it may even have Crashed the Kernel.

This was CentOS 6.5 I believe...whatever was current in the Summer of 2012.

Remember...Distributed != Usable. Red Hat distributes Infiniband stuff too, but everybody gets the Drivers and code from the Switch Vendors.

Perhaps that has gotten better too, but RHEL 5.5 never worked with QLogics switches back in 2010.

So Forge On Ahead. If you succeed I might take another look. But if you Die, you Heard It Here First.

JIM

P.S. So I guess the Challenge is to Find a Working Installation of cachefilesd.

----- Original Message -----
From: "Peter Larsen via Novalug" <novalug@firemountain.net>
To: novalug@firemountain.net
Sent: Friday, June 12, 2015 12:58:14 AM
Subject: Re: [Novalug] remote caching auto-syncing file system?

I haven't actually used it. It sounds pretty interesting though, so it's
on my list of things to try.
As to it's stability - it's included and supported by RHEL6 and RHEL7.
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/ch-fscache.html


I would however point out, that the project isn't exactly active. Most
updates I see are distribution specific changes since 2011. That doesn't
mean it's not working or that it won't be patched if needed. It just
means new features are probably not going to be added anytime soon.

-- 
Regards
  Peter Larsen




On 06/11/2015 07:24 PM, Mark Smith via Novalug wrote:
> Hey James, could you expand upon "Horribly Broken".  Those are certainly
> words to pay attention to, but in the interests of full disclosure,
> in what ways is it broken?  any particular version?  perhaps they fixed
> the broken bits recently?  how does it work with ext4 and NFS?  are these
> pictures accurate: http://lwn.net/Articles/275711/
>
>
> On Thu, Jun 11, 2015 at 09:47:21PM +0000, James Ewing Cottrell, III wrote:
>> Yes. Great Idea! But why do you think it isn't More Popular?
>>
>> Because IT's Horribly Broken! DO NOT EVER USE IT!
>>
>> Peter, Bryan, you wanna take this one?
>>
>> JIM
>>
>> ----- Original Message -----
>> From: "Mark Smith via Novalug" <novalug@firemountain.net>
>> To: "Novalug" <novalug@firemountain.net>
>> Sent: Wednesday, June 10, 2015 12:33:03 AM
>> Subject: Re: [Novalug] remote caching auto-syncing file system?
>>
>> can anyone talk about cachefilesd?  i think it caches local files and
>> works with ext4 already.  it's not clear how the data eventually gets
>> to the NFS server once it becomes avaialble though.
>>
>> On Wed, Jun 10, 2015 at 10:14:04AM +1200, Mark Smith via Novalug wrote:
>>> I am supposed to be using an NFS share which physically resides in another
>>> office.  for the most part it works okay, but it's obviously slower than
>>> local disk and more importantly the link goes down from time to time.
>>>
>>> i'd like to write to local disk and have it automatically synchronized
>>> to a another file system, immediately if possible, otherwise when it's
>>> available.  i've seen some specialized filesystems in the past that do
>>> exactly this sort of thing.
>>>
>>> Anyone got any recommendations for a remote caching file system such as this?
>> -- 
>> Hei konā mai
>> Mark Smith
>> mark@winksmith.com
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