Date: Thu, 21 Nov 2002 13:48:34 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: "BigBrother (BigB3)" <bigbrother@bonbon.net> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Performance degration of moving FFS hdd from a slow to a fast pc. Message-ID: <20021121194834.GB86807@dan.emsphone.com> In-Reply-To: <20021121140035.E29240-100000@bigb3server.bbcluster.gr> References: <20021121140035.E29240-100000@bigb3server.bbcluster.gr>
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In the last episode (Nov 21), BigBrother (BigB3) said: > I have a question about FFS filesystem. > > According to a paper about the design of UFS filesystem[1], if you > create the FFS filesystem on a slow cpu and then move it to a fast > cpu with a fast controller, theh the FFS wont perform efficient. > > This is justified because when the UFS is created having in mind the > speed of the system, in order to create the cyllinder group summary > information with optimal rotationally blocks [see page 7 of the > paper]. If somebody takes the hdd of the slow pc and put it on a much > faster pc, then it is reported that the throughput will drop > significantly because of lost disk revolutions. > > I would like to know if this is true. Can I move my hdd of my old > slow pc [intel 486] to a pentium III 600Mhz machine without > performance penatly, or its better to re-create the filesystem? Those optimizations were long since removed from the FFS code. The old C/H/S style of disk layout hasn't been used in 10 years (which means that FFS's logical cylinder groups do not correspond with the physical sylinders on the hard drive anymore), and CPUs are so fast that there is no need to "compensate" for a slow CPU anymore. You can put the disk in a faster PC and it will work optimally. -- Dan Nelson dnelson@allantgroup.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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