Date: Fri, 07 Dec 2007 15:16:30 +0100 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: readv: parallel or sequential? Message-ID: <fjbk9g$pua$1@ger.gmane.org> In-Reply-To: <20071207133700.GO10459@cicely12.cicely.de> References: <fjbb3v$n60$1@ger.gmane.org> <ad79ad6b0712070347s4a5d5bb2rc7adfdc54b107dac@mail.gmail.com> <868x46u0lz.fsf@ds4.des.no> <fjbh4h$f5s$1@ger.gmane.org> <20071207133700.GO10459@cicely12.cicely.de>
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[-- Attachment #1 --] Bernd Walter wrote: > I wonder if the kernel can read a single file in parallel, because > disk heads can't be on multiple positions at the same time. They can be in case of RAID0 and similar schemes. > ZFS does fill read cache in parallel if it knowns that there are enough > spindels, but in every other case the FS doesn't know about multiple > spindels. > In case of ZFS you don't have to care much about it in you application > because the next sequentiel fileread will use the previously parallel > prefilled cache. Yes, ZFS is supposed to be doing marvelous things with IO prediction and scheduling, but I think even basic "ladder" scheduling done in FreeBSD could in theory help in tight spots with multiple requests. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) iD8DBQFHWVXEldnAQVacBcgRAmfeAKDWpfk14QJvaSWHgOHFZM0L/5k4AwCdFhsX RTEJji9qv9pHDC07XEGEtpg= =IAO/ -----END PGP SIGNATURE-----
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