Re: ZFS RAIDZ1: resilvering at <17.3M/s => abyssal slow ...

Am Thu, 14 Dec 2017 15:46:17 +0100
Dimitry Andric <dim_at_FreeBSD.org> schrieb:

> On 14 Dec 2017, at 14:43, O. Hartmann <ohartmann_at_walstatt.org> wrote:
> > 
> > Am Thu, 14 Dec 2017 14:09:39 +0100
> > Daniel Nebdal <dnebdal_at_gmail.com> schrieb:  
> >> On Thu, Dec 14, 2017 at 12:48 PM, O. Hartmann <ohartmann_at_walstatt.org> wrote:  
> >>> I just started the rebuild/resilvering process and watch the pool crwaling at ~ 18
> >>> MB/s. At the moment, there is no load on the array, the host is a IvyBridge XEON
> >>> with 4 core/8 threads and 3,4 GHz and 16 GB of RAM. The HDDs are attached to a
> >>> on-board SATA II (300 MB/s max) Intel chip - this just for the record.
> >>> 
> >>> Recently, I switch on the "sync" attribute on most of the defined pools's zfs
> >>> filesystems
> >>> - I also use a SSD for ZIL/L2ARC caching, but it seems to be unused recently in
> >>> FreeBSD CURRENT's ZFS - this from a observers perspective only.
> >>> 
> >>> When scrubbing, I see recently also reduced performance on the pool, so I'm
> >>> wondering about the low throughput at the very moment when resilvering is in
> >>> progress.
> >>> 
> >>> If the "perspective" of "zpool status" is correct, then I have to wait after two
> >>> hours for another 100 hours - ~ 4 days? Ups ... I think there is something badly
> >>> misconfigured or missing.  
> ...
> >> This is kind of to be expected - for whatever reason, resilvers seem
> >> to go super slow at first and then speed up significantly. Just don't
> >> ask me how long "at first" is - I'd give it several (more) hours.  
> 
> Hopefully this will get better in the future, please read:
> 
> http://open-zfs.org/wiki/Scrub/Resilver_Performance
> 
> -Dimitry
> 

It has already been started to become better ;-)

After a while now, the throughput is at 128 MBytes/s and the estimated time decreased to
~ 8 h now - that is much more appreciable than 4 days ;-)

Kind regards,
Oliver


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O. Hartmann

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