From owner-freebsd-questions@freebsd.org Wed Jun 21 13:45:10 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B8362D90079 for ; Wed, 21 Jun 2017 13:45:10 +0000 (UTC) (envelope-from wblock@wonkity.com) Received: from wonkity.com (wonkity.com [67.158.26.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "wonkity.com", Issuer "wonkity.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 816606A8E1 for ; Wed, 21 Jun 2017 13:45:10 +0000 (UTC) (envelope-from wblock@wonkity.com) Received: from wonkity.com (localhost [127.0.0.1]) by wonkity.com (8.15.2/8.15.2) with ESMTPS id v5LDj28B070195 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 21 Jun 2017 07:45:02 -0600 (MDT) (envelope-from wblock@wonkity.com) Received: from localhost (wblock@localhost) by wonkity.com (8.15.2/8.15.2/Submit) with ESMTP id v5LDj22V070192; Wed, 21 Jun 2017 07:45:02 -0600 (MDT) (envelope-from wblock@wonkity.com) Date: Wed, 21 Jun 2017 07:45:02 -0600 (MDT) From: Warren Block To: Peter Ludikovsky cc: freebsd-questions@freebsd.org Subject: Re: New User, new server In-Reply-To: <800e15b2-d7f5-d339-bd77-862e9d0cab5b@ludikovsky.name> Message-ID: References: <800e15b2-d7f5-d339-bd77-862e9d0cab5b@ludikovsky.name> User-Agent: Alpine 2.21 (BSF 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (wonkity.com [127.0.0.1]); Wed, 21 Jun 2017 07:45:02 -0600 (MDT) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Jun 2017 13:45:10 -0000 On Tue, 20 Jun 2017, Peter Ludikovsky wrote: > 1) The new machine comes with a 128G SSD, in addition to the 2 4T HDDs > from the older server. I'd like to set up ZFS root, with a slice of the > SSD as ZIL and L2ARC, and the root mirrored across the SSD and the 2 > HDDs. Does this make sense, and if so what would be the ideal slice > layout? Or should I just use the whole SSD as ZIL/L2ARC? Don't mirror an SSD with hard drives. It will work, but cancels the benefit of the SSD. You don't say how much RAM the system has. Adding L2ARC without a decent amount of RAM is actually worse than nothing. ZIL is built in. An SSD to cache ZIL is called a SLOG. ZIL (and a SLOG) are for improving the speed of synchronous writes. Generally, that is rare unless you are using NFS and virtual machines. Also, a SLOG that is worthwhile usually needs a low-latency SSD that is used exclusively for that purpose. TLDR: unless you have at least 32GB or 64GB of RAM, adding L2ARC is questionable. A SLOG is usually only helpful if you have lots of synchronous writes, which is rare. Even then, it should be a fast, dedicated SSD just for that. http://doc.freenas.org/11/zfsprimer.html > 2) Moving data from the old machine. Can I run zfs send/receive to get > the ZFS on Linux datasets onto FreeBSD, or do I need to (r)sync? zfs send | zfs recv usually works. It depends on the feature flags on the originating system.