does btrfs have RAID I/O throughput (un)limiting sysctls, similar to md?

does btrfs have RAID I/O throughput (un)limiting sysctls, similar to md?

[0bo0]

i've a 4 drive array connected via a PCIe SATA card.

per OS (opensuse) default, md RAID I/O performance was being limited by,

  cat /proc/sys/dev/raid/speed_limit_min
    1000
  cat /proc/sys/dev/raid/speed_limit_max
    200000

changing,

  echo "dev.raid.speed_limit_min=100000" >> /etc/sysctl.conf
  echo "dev.raid.speed_limit_max=600000" >> /etc/sysctl.conf

enabled full/best I/O throughput.

does btrfs have a similar construct that I need to set/tweak for
maximum I/O throughput?

Re: does btrfs have RAID I/O throughput (un)limiting sysctls, similar to md?

[Daniel J Blueman]

On Sat, Feb 6, 2010 at 12:37 AM, 0bo0 <0.bugs.only.0@gmail.com> wrote:
> i've a 4 drive array connected via a PCIe SATA card.
>
> per OS (opensuse) default, md RAID I/O performance was being limited =
by,
>
> =A0cat /proc/sys/dev/raid/speed_limit_min
> =A0 =A01000
> =A0cat /proc/sys/dev/raid/speed_limit_max
> =A0 =A0200000
>
> changing,
>
> =A0echo "dev.raid.speed_limit_min=3D100000" >> /etc/sysctl.conf
> =A0echo "dev.raid.speed_limit_max=3D600000" >> /etc/sysctl.conf
>
> enabled full/best I/O throughput.

These proc entries affect just array reconstruction, not general I/O
performance/throughput, so affect just an edge-case of applications
requiring maximum latency/minimum throughout guarantees.
--=20
Daniel J Blueman
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Re: does btrfs have RAID I/O throughput (un)limiting sysctls, similar to md?

[0bo0]

On Sat, Feb 6, 2010 at 5:10 AM, Daniel J Blueman
<daniel.blueman@gmail.com> wrote:
> These proc entries affect just array reconstruction, not general I/O
> performance/throughput, so affect just an edge-case of applications
> requiring maximum latency/minimum throughout guarantees.

although i'd 1st seen the perf hit at the (re)construction stage, i
didn't recognize that the sysctls were limited to that case.

so, iiuc, btrfs has no such issues?

thanks for clarifying!

Re: does btrfs have RAID I/O throughput (un)limiting sysctls, similar to md?

[Martin Steigerwald]

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Am Samstag 06 Februar 2010 schrieben Sie:
> On Sat, Feb 6, 2010 at 5:10 AM, Daniel J Blueman
> 
> <daniel.blueman@gmail.com> wrote:
> > These proc entries affect just array reconstruction, not general I/O
> > performance/throughput, so affect just an edge-case of applications
> > requiring maximum latency/minimum throughout guarantees.
> 
> although i'd 1st seen the perf hit at the (re)construction stage, i
> didn't recognize that the sysctls were limited to that case.

Limiting rebuild throughput helps to have productively running 
applications getting their share of I/O during RAID rebuilds.
 
> so, iiuc, btrfs has no such issues?

Issues? I would call that a feature, not an issue.

-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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