From owner-freebsd-geom@FreeBSD.ORG Wed Jul 24 16:37:54 2013 Return-Path: Delivered-To: freebsd-geom@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 4F580AEA; Wed, 24 Jul 2013 16:37:54 +0000 (UTC) (envelope-from prvs=1917699425=killing@multiplay.co.uk) Received: from mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) (using TLSv1 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id BC7DC2C4D; Wed, 24 Jul 2013 16:37:53 +0000 (UTC) Received: from r2d2 ([82.69.141.170]) by mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) (MDaemon PRO v10.0.4) with ESMTP id md50005128155.msg; Wed, 24 Jul 2013 17:37:50 +0100 X-Spam-Processed: mail1.multiplay.co.uk, Wed, 24 Jul 2013 17:37:50 +0100 (not processed: message from valid local sender) X-MDDKIM-Result: neutral (mail1.multiplay.co.uk) X-MDRemoteIP: 82.69.141.170 X-Return-Path: prvs=1917699425=killing@multiplay.co.uk X-Envelope-From: killing@multiplay.co.uk Message-ID: From: "Steven Hartland" To: "Mark Felder" , References: <512DC7C043034F891F1012DA@Mail-PC.tdx.co.uk> <066EB1F973D44AAC951D4D47C577266F@multiplay.co.uk> <43FCB2933BDA7D36CA1719CD@Mail-PC.tdx.co.uk> <1374679655.8934.9223372036856590361.535ACEE3@webmail.messagingengine.com> <1374682388.24165.9223372036856608989.3CD1F525@webmail.messagingengine.com> Subject: Re: TRIM or no TRIM? Date: Wed, 24 Jul 2013 17:38:19 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Jul 2013 16:37:54 -0000 ----- Original Message ----- From: "Mark Felder" > On Wed, Jul 24, 2013, at 11:08, Steven Hartland wrote: >> >> Some people have said that, we've never seen it here, quite the opposite >> in fact. >> > > It's well documented. Here's a link to take you down the rabbit hole. > > http://lists.freebsd.org/pipermail/freebsd-stable/2013-February/072171.html I've seen that thread before, but it provides very little actual evidence which would mean it effects all usages. I even just tried the very test listed in Jeremy's post and I'm unable to reproduce even the slightest sutter, let alone a total I/O stall. http://lists.freebsd.org/pipermail/freebsd-fs/2011-October/012752.html Just to be clear I'm not saying there's no issue, just we've never experienced it and we use compression on a heavily used MySQL DB, our RRD processing machine and hundreds of game servers (which are highly latency sensitive). Clearly if your performing an additional translation of the data theirs going to be an CPU overhead for doing so but if said overhead is smaller that the gain in the reduction of data written or read from the device then your still going to end up with better performance with compression than without. Maybe we're lucky and our data matches the magic pattern or perhaps others are exadurating the negative effect, possibly a combination of the two I don't know ;-) Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.