From: antlists <antlists@youngman.org.uk>
To: "Finlayson, James M CIV (USA)" <james.m.finlayson4.civ@mail.mil>,
'Marcin Wanat' <marcin.wanat@gmail.com>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: [Non-DoD Source] Re: Slow initial resync in RAID6 with 36 SAS drives
Date: Wed, 1 Sep 2021 02:22:25 +0100 [thread overview]
Message-ID: <18699120-fb61-35e2-3b27-975773f3216a@youngman.org.uk> (raw)
In-Reply-To: <5EAED86C53DED2479E3E145969315A2385863D46@UMECHPA7D.easf.csd.disa.mil>
On 25/08/2021 11:28, Finlayson, James M CIV (USA) wrote:
> I'm not a person necessarily in the "know", but I mess with these in udev for SSDs:
> SUBSYSTEM=="block", ACTION=="add|change", KERNEL=="md*", ATTR{md/sync_speed_max}="2000000",ATTR{md/group_thread_cnt}="64", ATTR{md/stripe_cache_size}="8192"
>
> Guidance on why I change the values this way - educated "guess", as I'm an experienced practitioner at best and not someone that messes with the code......I've seen resync rates as high as 900MB/s sustained on my SSD mdraids, even though the SSDs should be able to sustain higher.....
Not raid, but I've picked up on comments (on LWN?) that certain
file-systems are very much "single threaded" in their behaviour. I
strongly suspect that md-raid predates common multi-cpu/multi-core
systems, and I've heard somewhere that md-raid doesn't thread that well.
It'd be nice to fix it, but retro-fitting existing code is a lot more
work than starting from scratch ...
Cheers,
Wol
next prev parent reply other threads:[~2021-09-01 1:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 9:28 Slow initial resync in RAID6 with 36 SAS drives Marcin Wanat
2021-08-25 10:06 ` Marcin Wanat
2021-08-25 10:28 ` [Non-DoD Source] " Finlayson, James M CIV (USA)
2021-09-01 1:22 ` antlists [this message]
2021-09-01 1:50 ` Guoqing Jiang
2021-09-01 5:19 ` Song Liu
2021-09-03 0:58 ` Song Liu
2021-09-03 2:56 ` Jens Axboe
2021-09-04 15:24 ` Marcin Wanat
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