From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id EF26C1381F3 for ; Tue, 17 Sep 2013 08:05:54 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 15E3EE0AF2; Tue, 17 Sep 2013 08:05:49 +0000 (UTC) Received: from svr-us4.tirtonadi.com (svr-us4.tirtonadi.com [69.65.43.212]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 0B401E0A9E for ; Tue, 17 Sep 2013 08:05:47 +0000 (UTC) Received: from mail-ve0-f180.google.com ([209.85.128.180]:39142) by svr-us4.tirtonadi.com with esmtpsa (TLSv1:RC4-SHA:128) (Exim 4.80.1) (envelope-from ) id 1VLqI8-003YiI-GG for gentoo-user@lists.gentoo.org; Tue, 17 Sep 2013 15:05:48 +0700 Received: by mail-ve0-f180.google.com with SMTP id jz11so3760873veb.25 for ; Tue, 17 Sep 2013 01:05:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=07JpxsIZABscMVVOX8Wja383WRjgdeyruUwdc6lCrgo=; b=LjJJhFx8UwIXZ/VrbbwmREReu4KNWM9HVrFXgXT3gWNs61sHzaHIo2g2XS9SjO49Qc LvmPJmfqFK/gAfY4L0MjkshlHnWDAqyUxNvZFv4iYYCE+lNSnYu9tt19eze0XiuFPzfO 5IZogLq3H3W3RhsPV7uSUT32fhquwQRt9+scnjTQfJZitkG2n2yr0yH+KPGZUDx8+ahp VDP8oZuhxXcS1qumGN47M+gm0mbVaNL6i2TqPmxomA2An5fwFMfL9XXsVDd6+OBKBm7w 7PYz4k0dWYBnxG519je53N5R3t/+cMhGXu30uuZ7LLir/6kptidxAQvvVKdW5pLk8MPD f75A== 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 MIME-Version: 1.0 X-Received: by 10.58.118.130 with SMTP id km2mr30884943veb.0.1379405147063; Tue, 17 Sep 2013 01:05:47 -0700 (PDT) Received: by 10.220.163.69 with HTTP; Tue, 17 Sep 2013 01:05:47 -0700 (PDT) In-Reply-To: References: Date: Tue, 17 Sep 2013 15:05:47 +0700 Message-ID: Subject: Re: [gentoo-user] ZFS From: Pandu Poluan To: gentoo-user Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - svr-us4.tirtonadi.com X-AntiAbuse: Original Domain - lists.gentoo.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - poluan.info X-Get-Message-Sender-Via: svr-us4.tirtonadi.com: authenticated_id: rileyer+pandu.poluan.info/only user confirmed/virtual account not confirmed X-Archives-Salt: d66ef869-248a-4023-ba71-edc61e283b3a X-Archives-Hash: cce843f30fdd2b36ce7bfb3cb2a6cf7d On Tue, Sep 17, 2013 at 2:20 PM, Grant wrote: > I'm convinced I need 3-disk RAID1 so I can lose 2 drives and keep > running. I'd also like to stripe for performance, resulting in > RAID10. It sounds like most hardware controllers do not support > 6-disk RAID10 so ZFS looks very interesting. > > Can I operate ZFS RAID without a hardware RAID controller? > Yes. In fact, that's ZFS' preferred mode of operation (i.e., it handles all redundancy by itself). > From a RAID perspective only, is ZFS a better choice than conventional > software RAID? > Yes. ZFS checksummed all blocks during writes, and verifies those checksums during read. It is possible to have 2 bits flipped at the same time among 2 hard disks. In such case, the RAID controller will never see the bitflips. But ZFS will see it. > ZFS seems to have many excellent features and I'd like to ease into > them slowly (like an old man into a nice warm bath). Does ZFS allow > you to set up additional features later (e.g. snapshots, encryption, > deduplication, compression) or is some forethought required when first > making the filesystem? > Snapshots is built-in from the beginning. All you have to do is create one when you want it. Deduplication can be turned on and off at will -- but be warned: You need HUGE amount of RAM. Compression can be turned on and off at will. Previously-compressed data won't become uncompressed unless you modify them. > It looks like there are comprehensive ZFS Gentoo docs > (http://wiki.gentoo.org/wiki/ZFS) but can anyone tell me from the real > world about how much extra difficulty/complexity is added to > installation and ongoing administration when choosing ZFS over ext4? > Very very minimal. So minimal, in fact, that if you don't plan to use ZFS as a root filesystem, it's laughably simple. You don't even have to edit /etc/fstab > Performance doesn't seem to be one of ZFS's strong points. Is it > considered suitable for a high-performance server? > > http://www.phoronix.com/scan.php?page=3Dnews_item&px=3DMTM1NTA > Several points: 1. The added steps of checksumming (and verifying the checksums) *will* give a performance penalty. 2. When comparing performance of 1 (one) drive, of course ZFS will lose. But when you build a ZFS pool out of 3 pairs of mirrored drives, throughput will increase significantly as ZFS has the ability to do 'load-balancing' among mirror-pairs (or, in ZFS parlance, "mirrored vdevs") Go directly to this post: http://phoronix.com/forums/showthread.php?79922-Benchmarks-Of-The-New-ZFS-O= n-Linux-EXT4-Wins&p=3D326838#post326838 Notice how ZFS won against ext4 in 8 scenarios out of 9. (The only scenario where ZFS lost is in the single-client RAID-1 scenario) > Besides performance, are there any drawbacks to ZFS compared to ext4? > 1. You need a huge amount of RAM to let ZFS do its magic. But RAM is cheap nowadays. Data... possibly priceless. 2. Be careful when using ZFS on a server on which processes rapidly spawn and terminate. ZFS doesn't like memory fragmentation. For point #2, I can give you a real-life example: My mail server, for some reasons, choke if too many TLS errors happen. So, I placed "Perdition" in to capture all POP3 connections and 'un-TLS' them. Perdition spawns a new process for *every* connection. My mail server has 2000 users, I regularly see more than 100 Perdition child processes. Many very ephemeral (i.e., existing for less than 5 seconds). The RAM is undoubtedly *extremely* fragmented. ZFS cries murder when it cannot allocate a contiguous SLAB of memory to increase its ARC Cache. OTOH, on another very busy server (mail archiving server using MailArchiva, handling 2000+ emails per hour), ZFS run flawlessly. No incident _at_all_. Undoubtedly because MailArchiva use one single huge process (Java-based) to handle all transactions, so no RAM fragmentation here. Rgds, --=20 FdS Pandu E Poluan ~ IT Optimizer ~ =E2=80=A2 LOPSA Member #15248 =E2=80=A2 Blog : http://pepoluan.tumblr.com =E2=80=A2 Linked-In : http://id.linkedin.com/in/pepoluan