From mboxrd@z Thu Jan 1 00:00:00 1970 From: Reindl Harald Subject: Re: disk initialize priority Date: Thu, 13 Apr 2017 12:05:03 +0200 Message-ID: <3f487a90-36ff-a319-977c-62d18ae65589@thelounge.net> References: <43e44c4b-37d6-9734-b323-5b432ef27d52@thelounge.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: de-CH Sender: linux-raid-owner@vger.kernel.org To: d tbsky Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Am 13.04.2017 um 11:58 schrieb d tbsky: > 2017-04-13 17:47 GMT+08:00 Reindl Harald : >> >> >> Am 13.04.2017 um 11:44 schrieb d tbsky: >>> >>> 2017-04-13 17:09 GMT+08:00 Reindl Harald : >>>> >>>> >>>> >>>> Am 13.04.2017 um 10:13 schrieb d tbsky: >>>>> >>>>> >>>>> Hi: >>>>> I just tried to install rhel 7.3 on a 4 disk raid6. it's a >>>>> minimal install but took 3 hours to finish. I found the disk >>>>> initialize speed is around 150MB/sec. in past the disk initialize >>>>> speed will down to slow speed when there are other disk IO, but it >>>>> seems not the case in rhel 7.3. >>>>> >>>>> I have check the below parameter: >>>>> cat /proc/sys/dev/raid/speed_limit_min -> 1000 >>>>> cat /proc/sys/dev/raid/speed_limit_max -> 200000 >>>>> >>>>> when the system is idle, the init speed is also about 150M/sec, so >>>>> the system is use all the power to init when there are other disk IO. >>>>> >>>>> is it normal? where should I check? >>>> >>>> >>>> >>>> sysctl.conf: >>>> dev.raid.speed_limit_min = 10000 >>>> dev.raid.speed_limit_max = 50000 >>>> >>>> sysctl -p >>>> >>>> and it will adjust itself within seconds - the same works if that values >>>> are >>>> too low and raid-check would take forever >>> >>> >>> hi: my problem is the speed is too high, not too low... >> >> and? >> >> you said it is at 200000 >> i showed you how to reduce it to 50000 or whatever you want > > hi: > sorry I didn't understand you correctly. thanks for the hint. I > will try to resolve the root cause of the problem the root cause is a default which is too large for your disks wqhile on the other hand if someone has a RAID10 with SSD disks it's even too low and you should just configure that for your needs and workload it's not only about how fast are your disks, it's also about your workload, there are times where i set it to 500000 to get the weekly raid-scrub as fast as possible when i don't heavily use the machine and on other days i slow it down dramatically because i need performance and don't care when the background task is finished it's also a difference between RAID1 or RAID10 when concurrency reads can be served by the other disk and the impact is not so big than on a RAID1