Date: Thu, 24 Sep 2015 19:17:13 +0300 From: Dmitrijs <war@dim.lv> To: Paul Kraus <paul@kraus-haus.org> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: zfs performance degradation Message-ID: <56042209.8040903@dim.lv> In-Reply-To: <8D1FF55C-7068-4AB6-8C0E-B4E64C1BB5FA@kraus-haus.org> References: <56019211.2050307@dim.lv> <37A37E9D-9D65-4553-BBA2-C5B032163499@kraus-haus.org> <56038054.5060906@dim.lv> <782C9CEF-BE07-4E05-83ED-133B7DA96780@kraus-haus.org> <56040150.90403@dim.lv> <60BF2FC3-0342-46C9-A718-52492303522F@kraus-haus.org> <560412B2.9070905@dim.lv> <8D1FF55C-7068-4AB6-8C0E-B4E64C1BB5FA@kraus-haus.org>
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2015.09.24. 18:44, Paul Kraus пишет: > On Sep 24, 2015, at 11:11, Dmitrijs <war@dim.lv> wrote: > >> Nope, no compression, no deduplication, only pure zfs. Even no prefetch, as it is not recommended for machines 4Gb RAM and below. > I am very surprised that ZFS is CPU limited on that system. My N54L has less CPU performance than that and I easily get 60 MB/sec via CIFS (Samba) from a Mac or Windows client. I also get about 60-70MB/sec via CIFS or ftp, but my aim is to be limited by network, so 100MB is wanted. Or, to understand why it is not possible on my config :) But simple dd of=/dev/null in the console shows me 110MB/sec... iozone gives me the same 100+Mb/sec both on read and write. That's one of the reasons I'm seeking advice in freebsd-questions@freebsd.org >> Now I'm not sure what configuration will make better performance for 4 HDD - raid10 or raid-z2? Or two separate mirrors? Need directions for scale things up in the future. > Of all the questions you have asked that one is the easiest to answer … a zpool which has 2 vdevs each of which is a 2-way mirror will have roughly double the performance of a zpool that has one vdev that is a 4 drive RAIDz2. Performance scales with the number of vdevs, not the number of drives. I know that is not obvious at first, but when you look at the design of ZFS (all top level vdevs are striped across) it makes perfect sense. > > So a 2 x 2-way mirror will be faster than a 4 drive RAIDz2. At a cost, the MTTDL (Mean Time To Data Loss) will be better for the RAIDz2 than the 2 x 2-way mirror. See Richard Ellings post here http://blog.richardelling.com/2010/02/zfs-data-protection-comparison.html for a comparison of relative MTTDL for ZFS configurations. > > Note that I use 3-way mirrors where I need _both_ performance and reliability and RAIDz2 where I need mostly reliability and performance is secondary. But … back when I was managing lots of data (2007 - 2012), I did use RADIz2 in production for critical data, but we had 22 top level vdevs, each a 5 drive RAIDz2 and 10 hot spares. Striping data across 22 RAIDz2 gave us the performance we needed with the reliability. Thanks, noted. Will educate myself in the given direction. >> Thought it would be sufficient, but now I'm in doubt. > I think that 4 GB is slightly low for a file server, but it should not be too bad. The CPU should be fine. What are the drives themselves ? [Because with only 4 GB RAM you _will_ feel the effect of drive performance, and it is random I/Ops that really matter for ZFS] 2x HGST HDN724040ALE640, 4Tb, 64Mb, 7200. I even ordered 8Gb RAM for tests, but they mistakenly delivered me 4Gb!.. > >> I can live with reduced performance for my 1st NAS, but would be nice to have clear performance requirements in mind for planing future storage boxes. >> >> I see QNAPs and Synology NAS, they use like 1Ghz CPU and 1Gb of RAM for 4 HDD, so either I'm doing it wrong, either those NASes don't have performance (or safety?) at all. > Do they calculate checksums for end-to-end data integrity ? > What is their performance like ? > > The data integrity and reliability features of ZFS do come at a cost. For example, yesterday I explored QNAP TS-451 official site: https://www.qnap.com/i/en/product/model.php?II=143&event=2 (Intel® Celeron® 2.41GHz dual-core processor, 1GB DDR3L, etc) and review: http://www.storagereview.com/qnap_ts451_nas_review 473euro Promised performance of the models is about 100Mb/sec, even up to 200Mb/sec but ok, it's marketing and pretty diagrams ;) I have no personal experience with them, so no idea about checksums and reliability. best regards, Dmitriy
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