From owner-freebsd-stable@FreeBSD.ORG Thu Jan 6 19:45:34 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CBA8A1065673 for ; Thu, 6 Jan 2011 19:45:34 +0000 (UTC) (envelope-from ml@my.gd) Received: from mail-fx0-f54.google.com (mail-fx0-f54.google.com [209.85.161.54]) by mx1.freebsd.org (Postfix) with ESMTP id 688968FC0C for ; Thu, 6 Jan 2011 19:45:32 +0000 (UTC) Received: by fxm16 with SMTP id 16so16258076fxm.13 for ; Thu, 06 Jan 2011 11:45:32 -0800 (PST) MIME-Version: 1.0 Received: by 10.223.100.5 with SMTP id w5mr8769245fan.20.1294343132020; Thu, 06 Jan 2011 11:45:32 -0800 (PST) Received: by 10.223.13.20 with HTTP; Thu, 6 Jan 2011 11:45:31 -0800 (PST) In-Reply-To: <4D25C760.4070703@digsys.bg> References: <4D1C6F90.3080206@my.gd> <4D21E679.80002@my.gd> <84882169-0461-480F-8B4C-58E794BCC8E6@my.gd> <488AE93A-97B9-4F01-AD0A-0098E4B329C3@my.gd> <4D25BF91.7070304@my.gd> <4D25C760.4070703@digsys.bg> Date: Thu, 6 Jan 2011 20:45:31 +0100 Message-ID: From: Damien Fleuriot To: Daniel Kalchev Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-stable@freebsd.org Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 06 Jan 2011 19:45:34 -0000 On 6 January 2011 14:45, Daniel Kalchev wrote: > For pure storage, that is a place you send/store files, you don't really > need the ZIL. You also need the L2ARC only if you read over and over again > the same dataset, which is larger than the available ARC (ZFS cache memory). > Both will not be significant for 'backup server' application, because it's > very unlikely to do lots of SYNC I/O (where separate ZIL helps), or serve > the same files back (where the L2ARC might help). > > You should also know that having large L2ARC requires that you also have > larger ARC, because there are data pointers in the ARC that point to the > L2ARC data. Someone will do good to the community to publish some reasonable > estimates of the memory needs, so that people do not end up with large but > unusable L2ARC setups. > > It seems that the upcoming v28 ZFS will help greatly with the ZIL in the > main pool.. > > You need to experiment with the L2ARC (this is safe with current v14 and v15 > pools) to see if your usage will see benefit from it's use. Experimenting > with ZIL currently requires that you recreate the pool. With the > experimental v28 code things are much easier. > I see, thanks for the pointers. The thing is, this will be a home storage (samba share, media server) box, but I'd also like to experiment a bit, and it seems like a waste to not try at least the cache, seeing I'll have a SSD at hand. If things go well, I may be able to recommend ZFS for production storage servers at work and I'd really like to know how the cache and ZIL work at that time ;)