From owner-freebsd-hackers Fri Jun 18 11: 6:17 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from atlrel1.hp.com (atlrel1.hp.com [156.153.255.210]) by hub.freebsd.org (Postfix) with ESMTP id A598115313 for ; Fri, 18 Jun 1999 11:05:29 -0700 (PDT) (envelope-from darrylo@sr.hp.com) Received: from srmail.sr.hp.com (srmail.sr.hp.com [15.4.45.14]) by atlrel1.hp.com (8.8.6 (PHNE_17135)/8.8.5tis) with ESMTP id OAA27375; Fri, 18 Jun 1999 14:03:38 -0400 (EDT) Received: from mina.sr.hp.com by srmail.sr.hp.com with ESMTP (1.37.109.16/15.5+ECS 3.3) id AA045749041; Fri, 18 Jun 1999 11:04:01 -0700 Received: from localhost (darrylo@mina.sr.hp.com [15.4.42.247]) by mina.sr.hp.com with ESMTP (8.8.6 (PHNE_17135)/8.7.3 TIS 5.0) id LAA12830; Fri, 18 Jun 1999 11:04:00 -0700 (PDT) Message-Id: <199906181804.LAA12830@mina.sr.hp.com> To: Greg Lehey Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: vinum performance Reply-To: Darryl Okahata In-Reply-To: Your message of "Fri, 18 Jun 1999 18:20:06 +0930." <19990618182006.C2863@freebie.lemis.com> Mime-Version: 1.0 (generated by tm-edit 1.1.1.1) Content-Type: text/plain; charset=US-ASCII Date: Fri, 18 Jun 1999 11:04:00 -0700 From: Darryl Okahata Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Greg Lehey wrote: > On Friday, 18 June 1999 at 1:14:20 -0700, Darryl Okahata wrote: > > > Possible marginally-related data point: with the 3.1-RELEASE vinum, > > and with striped drives (yes, I know the original user is using > > concatenated devices), I saw pretty bad write performance with the > > default filesystem frag size. Increasing the frag size (via newfs), > > increased performance substantially. > > That shouldn't have anything to do with it. If you see anything > unusual in Vinum performance, please tell me. It shouldn't, perhaps, have anything to do with it, but it did. I'm simply reporting empirical results, where I kept the stripe size constant and varied the filesystem frag size. I was able to get around a 2X improvement in write speed by increasing the frag size. Why, I don't know. I do know that I saw what I saw. ;-) This was, however, using 128K stripe sizes. Perhaps there's an interaction between small stripes and frag sizes? Also, I'm still stuck using the 3.1-RELEASE vinum. I want to upgrade to something newer, but I can't do so until I manage to backup my system (and I've got a lot of files to backup). ;-( > It's easy to come to > incorrect conclusions about the cause of performance problems, and > disseminating them doesn't help. Follow the links at It's not so much of a conclusion as a data point. I'm simply reporting what I saw. Note that I am NOT saying that varying the frag size is the most significant way of improving performance. I'm sure that you're correct in your recommendations. However, I was able to significantly affect write performace simply by changing the frag size. As I've said, I don't know why, but it happened. I don't know how reproducible this is; maybe it's related to rotational latencies, the particular drive type, drive firmware, CPU speed, etc.. I don't know -- but I do know that it happened, and I'm simply reporting a data point. This is just a single data point, and we all know how dangerous it is to extrapolate from a single data point. ;-) However, if others report their findings, we may or may not find a trend. -- Darryl Okahata darrylo@sr.hp.com DISCLAIMER: this message is the author's personal opinion and does not constitute the support, opinion, or policy of Hewlett-Packard, or of the little green men that have been following him all day. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message