From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mr4.vodafonemail.de (mr4.vodafonemail.de [145.253.228.164]) (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 DC35329CE5 for ; Wed, 12 Jun 2024 17:30:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=145.253.228.164 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718213411; cv=none; b=CvN5xj5ihHUQ8Kchm+AYVVCW7mkrKVTbZ+6q22et9vRSZG54ZRq2HHOT7IEiVkEHw2sWrfIqoEqWM5Bg9qc4DaoXMu++/l6LQvy9ldEiZJ1oRtYwtCWq0Ye/kN8dTtsxO2dihsKKSRiaK+KFXMjOz4xZC2GLpPUv+lCaTSHIF1s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718213411; c=relaxed/simple; bh=xMc2i+UsiHIE4fABWDUQbTIkaMBIsbSVtsDUcEsuUFs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LDoYNqC4pi3Y6EH1/U8RUXfYcc9N+p38ELjEPugFC3L1sqVDrCKEPyuClIZ/aQsDVUpG0CE1462u75PA3Zfs7QDNq3Le8M3x7coykzs24WrsWMcPvLXYUxBaAzfw9VlDWsdqu2eHh/3exSRSBpF9VkJLaA6C50X8vgeyrx6yrnQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=nexgo.de; spf=pass smtp.mailfrom=nexgo.de; dkim=pass (1024-bit key) header.d=nexgo.de header.i=@nexgo.de header.b=PMlkbcB+; arc=none smtp.client-ip=145.253.228.164 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=nexgo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=nexgo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=nexgo.de header.i=@nexgo.de header.b="PMlkbcB+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nexgo.de; s=vfde-mb-mr2-23sep; t=1718212976; bh=b3sQkTXGjigQQ+octqlbSxeWcI8yoA/DhT9YKY01Wrw=; h=Date:From:To:Subject:Message-ID:References:Content-Type: In-Reply-To:From; b=PMlkbcB+mRXTAHmnCPmG/CaIxM5bwgNenwkMJn3sNkkgZGRDNwvg7VAoqpAFedZ/A 5HeRDCPvAURq6ZsGdXxKQw7HIn6N6YGsSE0csMsKVOXC3tbRxwWskd0H78j2f6fTGu 3k1U5imODEBlTJ87Sfj18IgWBVrDxRyMlphKlJwA= Received: from smtp.vodafone.de (unknown [10.0.0.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by mr4.vodafonemail.de (Postfix) with ESMTPS id 4VzsnD3Dqgz1yGd; Wed, 12 Jun 2024 17:22:56 +0000 (UTC) Received: from lazy.lzy (p579d746a.dip0.t-ipconnect.de [87.157.116.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp.vodafone.de (Postfix) with ESMTPSA id 4Vzsn21ssRzHngB; Wed, 12 Jun 2024 17:22:43 +0000 (UTC) Received: from lazy.lzy (localhost [127.0.0.1]) by lazy.lzy (8.18.1/8.14.5) with ESMTPS id 45CHMgIN005337 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 12 Jun 2024 19:22:42 +0200 Received: (from red@localhost) by lazy.lzy (8.18.1/8.17.2/Submit) id 45CHMgjc005336; Wed, 12 Jun 2024 19:22:42 +0200 Date: Wed, 12 Jun 2024 19:22:42 +0200 From: Piergiorgio Sartor To: Reindl Harald Cc: Piergiorgio Sartor , linux-raid@vger.kernel.org Subject: Re: RAID-10 near vs. RAID-1 Message-ID: References: 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-Disposition: inline In-Reply-To: X-purgate-type: clean X-purgate: clean X-purgate-size: 1852 X-purgate-ID: 155817::1718212972-627B2BC3-64C003DA/0/0 On Wed, Jun 12, 2024 at 01:04:18AM +0200, Reindl Harald wrote: > > > Am 11.06.24 um 20:31 schrieb Piergiorgio Sartor: > > I'm setting up a system with 2 SSD M.2 (NVME). > > > > I was wondering if would it be better, performace > > wise, to have a RAID-10 near layout or a RAID-1. > > > > Looking around I found only one benchmark: > > > > https://strugglers.net/~andy/blog/2019/06/02/exploring-different-linux-raid-10-layouts-with-unbalanced-devices/ > > > > Which uses mixed SSD, NVME and SATA. > > > > Does anybody have any suggestions, links, or > > ideas on the topic? > > > > BTW, practically speaking, what's the difference, > > between the two RAIDs? > > i wouldn't even consider a RAID10 with two disks, especially with SSD and > practically you end with a unsupported RAID1 because there are no stripes > with 2 disks > Hi, thanks for the answer. I'm a bit confused here. What do you mean with "unsupported RAID1"? As far as I know, but please correct me if I'm wrong, a Linux md RAID-10 *near* layout, with 2 devices, has identical data distribution as a RAID-1 with 2 devices. Meaning the 2 devices are a mirror. The difference, if I understood it correctly, is that the RAID-10 has chunks, and hence stripes, while the RAID-1 does not have stripes. Furthermore, the read operation on RAID-10 are interleaved, delivering (for SSDs) double sequential read speed (for 2 devices), while the RAID-1 can handle two independent (one per device) read stream, each with single device reading speed. Of course, depending on the requirements, assuming what I wrote is correct, performances might be different. I was just wondering if anybody has some hints, some experience, some references, or, as you suggested, not to care at all. Thanks again, bye, -- piergiorgio