ZFS directory with a large number of files

[Hartmann, O.]

On 08/05/11 21:47, Patrick M. Hausen wrote:
> Hi, all,
>
> Am 05.08.2011 um 17:12 schrieb Christian Weisgerber:
>> Daniel Kalchev<daniel at digsys.bg>  wrote:
>>
>>> On 02.08.11 12:46, Daniel O'Connor wrote:
>>>> I am pretty sure UFS does not have this problem. i.e. once you
>>>> delete/move the files out of the directory its performance would be
>>>> good again.
>>> UFS would be the classic example of poor performance if you do this.
>> "Classic" indeed.  UFS dirhash has pretty much taken care of this
>> a decade ago.
> While dirhash is quite an improvement, it is definitely no silver bullet.
>
> When I asked Kirk McKusick at last year's EuroBSDCon if having
> a six-figure number of files in a single directory was a clever idea
> (I just had a customer who ran into that situation), he just smiled
> and shook his head.
>
> The directory in question was the typo3temp/pics directory that
> TYPO3 uses to scale images that are part of the website, so they
> are handed to the browser in exactly the size they are supposed
> to be rendered. The performance impact was quite heavy, because
> at some point requests started to pile up, PHP scripts did not finish
> in time, fcgi slots stayed used ... most of you will know that scenario.
> At some threshold a machine goes from "loaded, maybe a bit slow,
> but generally responsive" to "no f*ing way".
>
> Best regards,
> Patrick
>
I have similar situation here, but with a numerical simulation software, 
which drops for each timestep of integration a file of all integrated 
objects. Since the code is adopted and not very clever written in terms 
of doinf its I/O, I have to deal with this. While performing dynamical 
high resolution integrations of several hundreds of thousand objects 
over a time scale of 1 Ga produces even with a larger dump-delta creates 
a lot of files. making those files bigger results in a situation where 
they are hard to analyse, so its a tradeoff situation.
ZFS and UFS2 perform bad on this situation, UFS2 even more than ZFS, but 
also ZFS is still a pain in the ass.

Oliver