From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guoqing Jiang Subject: Re: [PATCH v3 00/11] md/raid5: set STRIPE_SIZE as a configurable value Date: Fri, 29 May 2020 14:22:30 +0200 Message-ID: <71f662d7-9aee-a130-c41d-67a691514ef6@cloud.ionos.com> References: <20200527131933.34400-1-yuyufen@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-raid-owner@vger.kernel.org To: Yufen Yu , song@kernel.org Cc: linux-raid@vger.kernel.org, neilb@suse.com, colyli@suse.de, xni@redhat.com, houtao1@huawei.com List-Id: linux-raid.ids On 5/29/20 1:49 PM, Yufen Yu wrote: >> The 4k rand write performance drops from 100MB/S to 15MB/S?! How >> about other >> io sizes? Say 16k, 64K and 256K etc, it would be more convincing if >> 64KB stripe >> has better performance than 4KB stripe overall. >> > > Maybe I have not explain clearly. Here, the fio test result shows that > 4KB > STRIPE_SIZE is not always have better performance. If applications > request > IO size mostly are bigger than 4KB, likely 1MB in test, set > STRIPE_SIZE with > a bigger value can get better performance. > > So, we try to provide a configurable STRIPE_SIZE, rather than fix > STRIPE_SIZE as 4096. Which means if you set stripe size to 64KB then you should guarantee the io size should always bigger then 1MB, right? Given that, I don't think it makes lots of sense. Anyway, just my $0.02. Thanks, Guoqing