From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id 8B3D9138350 for ; Mon, 4 May 2020 07:51:38 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 36977E0A92; Mon, 4 May 2020 07:50:59 +0000 (UTC) Received: from www69.your-server.de (www69.your-server.de [213.133.104.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id CDB17E0A7C for ; Mon, 4 May 2020 07:50:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=konstantinhansen.de; s=default1908; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:To: Subject:Sender:Reply-To:Cc:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uYFVSoPCi0rh5Gpq1qlR/rIZ76ktvFFdt70Hdz8OFLY=; b=tWPPpCvdP4VWmTrq2pWFyFcxj gUHIADqTusGwsM+SQyB86e/MXT4KMoUqCADVV5e5MgnXCvV0TG0Gx1tSz7nxMGYSzWpwyrCARy/uu A857WWATzdol4c5TZ5hJwMlI4V6Bd434mcCZ174//BRwUjV8wX95AIDQFwezztVUfQHRZyU3aSYYS jn1tH9TkZ2PMJWiUt0fN+oLBjR290zvbaOTEpN9eWKg/VwBYKMnR8W80Vm5jYI7fgBTJnWNusFr+D mrgsrAB1iSzdM9ebi9t7TUO2vRnZoaegz5NgsGcU/IxaoFIeJm0dTTIzk6DhBEFrOGqDPAfC4Mg77 DuFluzWtg==; Received: from pd9eed451.dip0.t-ipconnect.de ([217.238.212.81] helo=[192.168.2.102]) by www69.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1jVVsI-0000Jp-KR for gentoo-user@lists.gentoo.org; Mon, 04 May 2020 09:50:50 +0200 Subject: Re: [gentoo-user] which linux RAID setup to choose? To: gentoo-user@lists.gentoo.org References: <2251dac1-92cd-7c3b-97ea-6a061fe01eb0@users.sourceforge.net> From: hitachi303 Message-ID: <49b1d819-0e85-3bb8-a495-417677aaf15e@konstantinhansen.de> Date: Mon, 4 May 2020 09:50:50 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: de-DE Content-Transfer-Encoding: 7bit X-Authenticated-Sender: gentoo-user@konstantinhansen.de X-Virus-Scanned: Clear (ClamAV 0.102.2/25801/Sun May 3 14:08:15 2020) X-Archives-Salt: ade5da21-8c09-444e-8702-1c2862437d1e X-Archives-Hash: d4ff3bfb21ed2ab42639f5a69a36a423 Am 04.05.2020 um 02:46 schrieb Rich Freeman: > On Sun, May 3, 2020 at 6:50 PM hitachi303 > wrote: >> >> The only person I know who is running a really huge raid ( I guess 2000+ >> drives) is comfortable with some spare drives. His raid did fail an can >> fail. Data will be lost. Everything important has to be stored at a >> secondary location. But they are using the raid to store data for some >> days or weeks when a server is calculating stuff. If the raid fails they >> have to restart the program for the calculation. > > So, if you have thousands of drives, you really shouldn't be using a > conventional RAID solution. Now, if you're just using RAID to refer > to any technology that stores data redundantly that is one thing. > However, if you wanted to stick 2000 drives into a single host using > something like mdadm/zfs, or heaven forbid a bazillion LSI HBAs with > some kind of hacked-up solution for PCIe port replication plus SATA > bus multipliers/etc, you're probably doing it wrong. (Really even > with mdadm/zfs you probably still need some kind of terribly > non-optimal solution for attaching all those drives to a single host.) > > At that scale you really should be using a distributed filesystem. Or > you could use some application-level solution that accomplishes the > same thing on top of a bunch of more modest hosts running zfs/etc (the > Backblaze solution at least in the past). > > The most mainstream FOSS solution at this scale is Ceph. It achieves > redundancy at the host level. That is, if you have it set up to > tolerate two failures then you can take two random hosts in the > cluster and smash their motherboards with a hammer in the middle of > operation, and the cluster will keep on working and quickly restore > its redundancy. Each host can have multiple drives, and losing any or > all of the drives within a single host counts as a single failure. > You can even do clever stuff like tell it which hosts are attached to > which circuit breakers and then you could lose all the hosts on a > single power circuit at once and it would be fine. > > This also has the benefit of covering you when one of your flakey > drives causes weird bus issues that affect other drives, or one host > crashes, and so on. The redundancy is entirely at the host level so > you're protected against a much larger number of failure modes. > > This sort of solution also performs much faster as data requests are > not CPU/NIC/HBA limited for any particular host. The software is > obviously more complex, but the hardware can be simpler since if you > want to expand storage you just buy more servers and plug them into > the LAN, versus trying to figure out how to cram an extra dozen hard > drives into a single host with all kinds of port multiplier games. > You can also do maintenance and just reboot an entire host while the > cluster stays online as long as you aren't messing with them all at > once. > > I've gone in this general direction because I was tired of having to > try to deal with massive cases, being limited to motherboards with 6 > SATA ports, adding LSI HBAs that require an 8x slot and often > conflicts with using an NVMe, and so on. So you are right. This is the way they do it. I used the term raid to broadly. But still they have problems with limitations. Size of room, what air conditioning can handle and stuff like this. Anyway I only wanted to point out that there are different approaches in the industries and saving the data at any price is not always necessary.