From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from nt.romanrm.net (nt.romanrm.net [185.213.174.59]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 00A2E19DF53 for ; Fri, 7 Mar 2025 20:47:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.213.174.59 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741380446; cv=none; b=m31V1rFXpa4DZaDPN0ZreRGHB3EdgsUrcMrZA/0SZNVoz16NtiN362ks0rJY8g3pilYB1jTPAlm+fy7xWJzGuJoVh4jTfC4/x6fItSgpy7pSdQLacfr4M2bnROg1p51G9PGhIT+2Aw+elKbj3emChkzz3kvPfVP1F8oHbKQq1rQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741380446; c=relaxed/simple; bh=l/KxW8DM5zUxiS1NTIvmKBXnFRw3HvRG8sEXpgIcQNk=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=quRE7DmWcDszsEbU2aWh5Q+oP0CV91Zl0PITBUlwcqWlyO4uC/fw3aiNbPzEdHb4IXxM68Q3hP4hTJklhiYuTsinMFMxpVdy/odCAxVZyY5L10jBNPP5DSZiy2rKgl+9EC7Cout4g7vRPaqWcUST99fbOtt7PsPKvCORLSDcjuA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=romanrm.net; spf=pass smtp.mailfrom=romanrm.net; arc=none smtp.client-ip=185.213.174.59 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=romanrm.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=romanrm.net Received: from nvm (umi.2.romanrm.net [IPv6:fd39:a37d:999f:7e35:7900:fcd:12a3:6181]) by nt.romanrm.net (Postfix) with SMTP id 423C540F47; Fri, 7 Mar 2025 20:47:19 +0000 (UTC) Date: Sat, 8 Mar 2025 01:47:18 +0500 From: Roman Mamedov To: Roger Heflin Cc: David Hajes , "linux-raid@vger.kernel.org" Subject: Re: RAID 5, 10 modern post 2020 drives, slow speeds Message-ID: <20250308014718.24418feb@nvm> In-Reply-To: References: <20250307234753.473dc4b5@nvm> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 7 Mar 2025 14:42:24 -0600 Roger Heflin wrote: > I put an external bitmap on a raid1 SSD and that seemed to speed up my > writes. I am not sure if external bitmaps will continue to be > supported as I have seen notes that I don't exactly understand for > external bitmaps, and I have to reapply the external bitmap on each > reboot for my arrays which has some data loss risks in a crash case > with a dirty bitmap. > > This is the command I used to set it up. > mdadm --grow --force --bitmap=/mdraid-bitmaps/md15-bitmap.img /dev/md15 In this case the result cited seems to have shown the bitmap is not the issue. I remember seeing patches or talks to remove external bitmap support, too. In my experience the internal bitmap with a large enough chunk size does not slow down the write speed that much. Try a chunk size of 256M. Not sure how high it's worth going before the benefits diminish. -- With respect, Roman