ionice

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ionice

Postposted on Fri May 30, 2014 9:42 am

In a thread in General Hardware viewtopic.php?f=29&t=93996 I started talking about ionice and how it stops hard drive systems from slowing to a crawl. I don't want to derail that topic so starting a new thread here to continue the conversation.

just brew it! wrote:Hmm... the documentation implies that ionice requires the CFQ I/O scheduler. Ubuntu uses the deadline scheduler by default, so I assume it would have no effect unless I force use of the CFQ scheduler? (I do know how to configure the I/O scheduler, so that's not a big deal.
I just checked and whilst there is a bug saying exactly this https://bugs.launchpad.net/ubuntu/+sour ... ug/1310402, it turns out that my machine is defaulting to the CFQ scheduler
Code: Select all
$ uname -rv
3.2.0-63-generic #95-Ubuntu SMP Thu May 15 23:05:57 UTC 2014
$ grep DEFAULT_IOSCHED /boot/config-3.2.0-63-generic
CONFIG_DEFAULT_IOSCHED="cfq"
$


just brew it! wrote:More problematic is that it also sounds like ionice does not work with MD (software RAID) arrays. I typically use software RAID-1 for mechanical HDDs, so ionice may be a non-starter...
Can't help with that :)
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Re: ionice

Postposted on Fri May 30, 2014 10:19 am

They changed the default in more recent kernels. I'm running 12.04, but with the 12.04.4 kernel and X stack (13.10-derived HWE packages). I believe deadline has been the default since 13.x?

Edit:
Code: Select all
$ uname -r; grep DESCRIPTION /etc/lsb-release
3.11.0-22-generic
DISTRIB_DESCRIPTION="Ubuntu 12.04.4 LTS"
$ grep CONFIG_DEFAULT_IOSCHED /boot/config-`uname -r`
CONFIG_DEFAULT_IOSCHED="deadline"
$
(this space intentionally left blank)
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Re: ionice

Postposted on Fri May 30, 2014 12:46 pm

Ah, I'm still on the original 12.04 line of kernels.

It's worth playing with, an ionice to idle seems to have no effect on interactive tasks and is cheaper than an SSD. You don't get the seek times of an SSD though. :D
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Re: ionice

Postposted on Fri May 30, 2014 1:36 pm

Yeah, but then I would need to forego the RAID-1. My current preferred configuration is a small-ish (and therefore relatively affordable) SSD for the system and any other files that get signficant benefit from the accelerated access (e.g. virtual drives for heavily used VMs), and a pair of HDDs in RAID-1 for /home.

Life is full of trade-offs. :wink:
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