Date: Thu, 9 Jul 2009 15:43:02 +0200 From: "Patrick M. Hausen" <hausen@punkt.de> To: "Tonix (Antonio Nati)" <tonix@interazioni.it> Cc: freebsd-stable@freebsd.org Subject: Re: ZFS - thanks Message-ID: <20090709134302.GA50485@hugo10.ka.punkt.de> In-Reply-To: <4A55EEEC.3030007@interazioni.it> References: <20090709112512.GA44158@hugo10.ka.punkt.de> <73a41d4b72d62b0bfe3d0fb7206376a8.squirrel@cygnus.homeunix.com> <20090709123434.GC46563@hugo10.ka.punkt.de> <4A55EEEC.3030007@interazioni.it>
next in thread | previous in thread | raw e-mail | index | archive | help
Hello, On Thu, Jul 09, 2009 at 03:21:48PM +0200, Tonix (Antonio Nati) wrote: > I see a lot of people advicing to use ZFS RAID instead of HW RAID. > I'm going to use HP duplicated iSCSI subsystems, which have autonomous > RAID, so I'm confused about this advice. > Following the ZFS RAID stream, should I keep each disk alone in iSCSI and > let the ZFS make the RAID job? > Should not HW RAID to be (a lot) more efficient? You cannot escape the poor write performance of RAID 5 and comparable setups with or without hardware. No matter how much you cache, one time a block must be written to disk. And for RAID 1 or 1+0 we found the impact on modern CPUs negligible. So we switched to GEOM for mirroring a long time ago for one simple reason: hardware replacement. With a "hardware RAID" you need the precise brand and model of the controller (worst case) to read a disk with valuable data on it in case of a complete machine failure and replacement. What, if that's not avaliable any more? With software you just need an arbitrary machine with the matching HDD interface (P-ATA, S-ATA, SCSI, ...) This is my first attempt at software RAID-other-than-1, but I'm really pleased with the results so far. The system is a Fujitsu (former Fujitsu Siemens) SX 40 JBOD with a SAS host interface and SAS or S-ATA disks. You can daisy chain 3 of these boxes with twelve disks each to one server. The host adapter in my server doesn't have any RAID functions. LSI something, easily replaced. Reasonably priced, nice, scalable solution for our needs. It's a datastore, so it doesn't do anything but backup and restore. I would not use ZFS for something that needs to be "up" 24x7 just yet. We had a couple of crashes before we changed some memory parameters. Kind regards, Patrick -- punkt.de GmbH * Kaiserallee 13a * 76133 Karlsruhe Tel. 0721 9109 0 * Fax 0721 9109 100 info@punkt.de http://www.punkt.de Gf: Jürgen Egeling AG Mannheim 108285
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20090709134302.GA50485>