Date: Tue, 23 Aug 2011 11:52:09 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Re: ZFS installs on HD with 4k physical blocks without any warning as on 512 block size device Message-ID: <j2vt89$qap$1@dough.gmane.org> In-Reply-To: <20110823012326.GA29658@server.vk2pj.dyndns.org> References: <4E4D50CD.5080806@rawbw.com> <CAFHbX1K%2BRuzBKouAbN0%2BSCOSAkGNdgMzC92YN7GeKn_pD=J=tg@mail.gmail.com> <CAO1bj=ZHC0ZMtrQKr3DV8E3rP3gTMHxdF3J2EPAD3wR5dqN%2BkA@mail.gmail.com> <j2tbvk$k1q$1@dough.gmane.org> <20110823012326.GA29658@server.vk2pj.dyndns.org>
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On 23/08/2011 03:23, Peter Jeremy wrote: > On 2011-Aug-22 12:45:08 +0200, Ivan Voras<ivoras@freebsd.org> wrote: >> It would be suboptimal but only for the slight waste of space that would >> have otherwise been reclaimed if the block or fragment size remained 512 >> or 2K. This waste of space is insignificant for the vast majority of >> users and there are no performance penalties, so it seems that switching >> to 4K sectors by default for all file systems would actually be a good idea. > > This is heavily dependent on the size distribution. I can't quickly > check for ZFS but I've done some quick checks on UFS. The following > are sizes in MB for my copies of the listed trees with different UFS > frag size. These include directories but not indirect blocks: > > 1b 512b 1024b 2048b 4096b > 4430 4511 4631 4875 5457 /usr/ncvs > 4910 5027 5181 5499 6133 Old FreeBSD SVN repo > 299 370 485 733 1252 /usr/ports cheched out from CVS > 467 485 509 557 656 /usr/src 8-stable checkout from CVS > > Note that the ports tree grew by 50% going from 1K to 2K frags and > will grow by another 70% going to 4KB frags. Similar issues will > be seen when you have lots of small file. I agree but there are at least two things going for making the increase anyway: 1) 2 TB drives cost $80 2) Where the space is really important, the person in charge usually knows it and can choose a non-default size like 512b fragments.
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