Date: Fri, 17 Jan 2014 13:17:51 -0800 From: Kevin Oberman <rkoberman@gmail.com> To: paul beard <paulbeard@gmail.com> Cc: FreeBSD Ports <ports@freebsd.org>, bart@tapolsky.net.ua Subject: Re: clonehdd followup Message-ID: <CAN6yY1v3yjeizU7jKobE=twq4-YWko92uw2iCnKprE3Ts6gxJg@mail.gmail.com> In-Reply-To: <CAMtcK2rdKdnHT1Lai8u5g5FnSZmvhBdPq_6iR_J8pjBsSJgqDQ@mail.gmail.com> References: <CAMtcK2rJOQz1dh9wjU5xKvTkPv%2B-U_cgzmyfbtYPF%2BpimBpKdg@mail.gmail.com> <CAMtcK2rdKdnHT1Lai8u5g5FnSZmvhBdPq_6iR_J8pjBsSJgqDQ@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Jan 17, 2014 at 8:51 AM, paul beard <paulbeard@gmail.com> wrote: > Grr. The return key should not be the same as Send. > > I had some problems with clonehdd that turned out to be hardware issued: = my > disks has somehow defaulted to PIO4 from UDMA which made this process run > so slow it would just quit with finishing. > > Now things are more what I expect, completing a clone of my root disk in > 524 minutes, down from multiple days=E2=80=A6 > > But it still seems slow if the disks are 1.5Gb/sec SATA disks. Looking > around, it looks like this might be useful to speed things up. > > > http://www.wonkity.com/~wblock/docs/html/disksetup.html > > -- > Paul Beard / www.paulbeard.org/ > Remember that 1.5GB/s is the speed supported by the electronics and the cache. It is not the speed that the disk actually reads or writes from/to the platters. When cloning, very little of the data is in cache, so you are generally limited by seek times (should be minimal if the code is well done) and rotational speed. The really then boils down to transfer speeds are going ot be close to what is possible with the rotational speed. Since I lack specifics on your disk drive, you'll have to do the arithmetic. It will only be approximate because of the tricks disks use for spatial optimization, but it won't be 1.5GB/s. Also be aware that disabling write cache will significantly reduce performance. (It should be "on" by default.) N.B. Several statements above are incomplete or slightly inaccurate. I think they are close enough for this discussion and being both complete and accurate would make this message way too long. --=20 R. Kevin Oberman, Network Engineer, Retired E-mail: rkoberman@gmail.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAN6yY1v3yjeizU7jKobE=twq4-YWko92uw2iCnKprE3Ts6gxJg>