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 284531381F3 for ; Tue, 17 Sep 2013 16:32:39 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 05EEBE0C00; Tue, 17 Sep 2013 16:32:33 +0000 (UTC) Received: from mail0131.smtp25.com (mail0131.smtp25.com [75.126.84.131]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 0F551E0BEF for ; Tue, 17 Sep 2013 16:32:31 +0000 (UTC) Received: from ccs.covici.com (d-out-001.smtp25.com [67.228.158.174] (may be forged)) by d-out-001.smtp25.com (8.14.2/8.14.2) with ESMTP id r8HGWU34005521 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Tue, 17 Sep 2013 12:32:30 -0400 Received: from ccs.covici.com (localhost [127.0.0.1]) by ccs.covici.com (8.14.7/8.14.5) with ESMTP id r8HGWT6u020168 for ; Tue, 17 Sep 2013 12:32:29 -0400 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] ZFS In-reply-to: References: Comments: In-reply-to Pandu Poluan message dated "Tue, 17 Sep 2013 15:05:47 +0700." X-Mailer: MH-E 8.2; nmh 1.3; GNU Emacs 23.4.1 Date: Tue, 17 Sep 2013 12:32:29 -0400 Message-ID: <20167.1379435549@ccs.covici.com> From: covici@ccs.covici.com X-SpamH-OriginatingIP: 70.109.53.110 X-SpamH-Filter: d-out-001.smtp25.com-r8HGWU34005521 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-Archives-Salt: c4ba9d4b-16a2-44c7-850d-32c8c22856b3 X-Archives-Hash: ac898d0e1c332aa60c54e200a0121b83 Pandu Poluan wrote: > 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=news_item&px=MTM1NTA > > > > 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-On-Linux-EXT4-Wins&p=326838#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. Spo do I need that overlay at all, or just emerge zfs and its module? Also, I now have lvm volumes, including root, but not boot, how to convert and do I have to do anything to my initramfs? -- Your life is like a penny. You're going to lose it. The question is: How do you spend it? John Covici covici@ccs.covici.com