[OpenIndiana-discuss] Mitigating the performance impact of scrub

[Reginald Beardsley]

Where would I find information about the kernel level tunable parameters?  Are there specific parameters you have in mind?

What I'm seeing is very slow loads of  OpenOffice.  It's certainly not quick under the best of circumstances, but this was particularly slow.  I just needed to read a bunch of 5-6 MB .xls files and export them as .csv files.

Reg

--- On Thu, 9/27/12, Richard Elling <richard.elling at richardelling.com> wrote:

> From: Richard Elling <richard.elling at richardelling.com>
> Subject: Re: [OpenIndiana-discuss] Mitigating the performance impact of scrub
> To: "Discussion list for OpenIndiana" <openindiana-discuss at openindiana.org>
> Date: Thursday, September 27, 2012, 1:15 PM
> On Sep 27, 2012, at 8:44 AM, Reginald
> Beardsley <pulaskite at yahoo.com>
> wrote:
> 
> > The only thing google turned up was "stop the scrub if
> it impacts performance too badly" which is not really all
> that helpful. Or ways to speed up scrubs & resilvers.
> 
> On modern ZFS implementations, scrub I/O is throttled to
> avoid impacting application I/O
> performance. There are some kernel-level tunable parameters
> that can be adjusted, but
> AFAIK, nobody has done any characterization studies.
> 
> > 
> > In my case, I'd like to be able to run a scrub and have
> all the performance hits taken by the scrub process if the
> system has other loads.  I care that the scrub runs,
> but not how fast.
> > 
> > From observed behavior, it appears that the scrub is
> consuming too large a share of DRAM (12 GB in this
> case).  Is that correct and if so, is there a way to
> limit the proportion of memory used by the scrub process?
> 
> Data is cached in the ARC, but scrub data is placed in the
> MRU/LRU side of the ARC
> and shouldn't impact the MFU side. In most cases, the memory
> usage during a scrub
> is not a problem. Have you seen a different behaviour?
>  -- richard
> 
> > I'd like to be able to schedule scrubs regularly, but
> the present behavior would require predicting when I didn't
> want to use the system for work.
> > 
> > Thanks,
> > Reg
> 
> --
> illumos Day & ZFS Day, Oct 1-2, 2012 San Fransisco 
> www.zfsday.com
> Richard.Elling at RichardElling.com
> +1-760-896-4422
> 
> 
> 
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