From owner-freebsd-fs@FreeBSD.ORG Fri Feb 15 09:24:57 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 4B2B9A29 for ; Fri, 15 Feb 2013 09:24:57 +0000 (UTC) (envelope-from daniel@digsys.bg) Received: from smtp-sofia.digsys.bg (smtp-sofia.digsys.bg [193.68.3.230]) by mx1.freebsd.org (Postfix) with ESMTP id AD256CD6 for ; Fri, 15 Feb 2013 09:24:56 +0000 (UTC) Received: from [10.5.0.53] ([87.250.40.22]) (authenticated bits=0) by smtp-sofia.digsys.bg (8.14.5/8.14.5) with ESMTP id r1F9A88H032270 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Fri, 15 Feb 2013 11:10:08 +0200 (EET) (envelope-from daniel@digsys.bg) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: Crazy ZFS ZIL options: md(4) umass(4) From: Daniel Kalchev In-Reply-To: Date: Fri, 15 Feb 2013 10:10:09 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: <43BC680B-4FC6-4CDB-A590-12ACC78959B7@digsys.bg> References: To: grarpamp X-Mailer: Apple Mail (2.1499) Cc: freebsd-fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Feb 2013 09:24:57 -0000 In short, don't. ZIL is not a cache. ZIL is there for you to recover transactions in case = of a crash. It is your safety net. If you don't have low latency SSD, put it on separate spinning disk, but = by all means never on RAM and USB only as a last resort, because USB is = slow for most uses and it is also extremely unreliable. Use the RAM for ARC, it will provide more performance. Daniel On Feb 15, 2013, at 10:00 AM, grarpamp wrote: > I have thousands of small files being written most under 8KiB, they > either end up being removed or combined in various ways to > produce a set of data that is stored long term. I also have > tens of 10-50MiB files similarly, but rarely. It's not fully clear > to me the benefits of a split ZIL. Some say a split ZIL will ward > off some fragmentation, which pushing over 80% I'm sure to see > otherwise. Plus a speed boost if on faster media. And maybe > even no need to commit some ZIL to disk as small files are > removed before ZFS decides to aggregate? >=20 > Anyway, use case aside, I can put 1GiB of ram as ZIL.Same for 32GiB = USB. > RAM is obviously fast and power fail prone. > USB is slow and power safe. > Either could be mirrored, 2xRAM, 2xUSB. >=20 > - If I lose power on RAM, will the disk still be consistent? > - What data integrity does ZIL have? None? ZFS dataset's sha256? > - Any production experiences with this crazy ideas? >=20 > Thx. > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"