From: Guoqing Jiang <guoqing.jiang@linux.dev>
To: antlists <antlists@youngman.org.uk>,
"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 09:50:55 +0800 [thread overview]
Message-ID: <f8eee1bd-673e-dd68-d393-5e1c07415117@linux.dev> (raw)
In-Reply-To: <18699120-fb61-35e2-3b27-975773f3216a@youngman.org.uk>
On 9/1/21 9:22 AM, antlists wrote:
> 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.
Yes and no, raid5 does support multi-threading if group_thread_cnt > 0,
but IIUC, only one thread (mdx_resync) deals with resync IO.
Thanks,
Guoqing
next prev parent reply other threads:[~2021-09-01 1:51 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
2021-09-01 1:50 ` Guoqing Jiang [this message]
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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