Date: Thu, 22 Jul 2010 19:54:22 +0930 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Adam Vande More <amvandemore@gmail.com> Cc: Charles Sprickman <spork@bway.net>, freebsd-stable <freebsd-stable@freebsd.org>, Dan Langille <dan@langille.org> Subject: Re: Using GTP and glabel for ZFS arrays Message-ID: <5609C94D-CDD7-4798-9E60-7686086999A1@gsoft.com.au> In-Reply-To: <AANLkTilK8bEfeJB7lw68DKeT6Qih7uy9nAtxF1pKuom5@mail.gmail.com> References: <4C47B57F.5020309@langille.org> <AANLkTimbYGpC0aYGnE61J5ZopQVD9m8hrz07CZAnsvsq@mail.gmail.com> <alpine.OSX.2.00.1007220009210.33454@hotlap.local> <AANLkTilK8bEfeJB7lw68DKeT6Qih7uy9nAtxF1pKuom5@mail.gmail.com>
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On 22/07/2010, at 13:59, Adam Vande More wrote: > To be clear, we are talking about data partitions, not the boot one. > Difficult for me to explain concisely, but basically it has to do with = seek > time. A mis-aligned partition will almost always have an extra seek = for > each standard seek you'd have on aligned one. There have been some > discussions about in the archives, also this is not unique to FreeBSD = so > google will have a more detailed and probably better explanation. Newer disks have 4kb sectors internally at least, and some expose it to = the OS. If you create your partitions unaligned to this every read and write = will involve at least one more sector than it would otherwise and that = hurts performance. The disks which don't expose it have a jumper which offsets all accesses = to Windows XP's performance doesn't take a dive but I'm not sure if that = helps FreeBSD. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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