Date: Sun, 16 Nov 2008 22:06:42 -0800 From: Matt Simerson <matt@corp.spry.com> To: freebsd-fs@freebsd.org Cc: freebsd-hardware@freebsd.org Subject: Re: Areca vs. ZFS performance testing. Message-ID: <F55CD13C-8117-4D34-9C35-618D28F9F2DE@spry.com> In-Reply-To: <4920E1DD.7000101@dannysplace.net> References: <490A782F.9060406@dannysplace.net> <20081031033208.GA21220@icarus.home.lan> <490A849C.7030009@dannysplace.net> <20081031043412.GA22289@icarus.home.lan> <490A8FAD.8060009@dannysplace.net> <491BBF38.9010908@dannysplace.net> <491C5AA7.1030004@samsco.org> <491C9535.3030504@dannysplace.net> <CEDCDD3E-B908-44BF-9D00-7B73B3C15878@anduin.net> <4920E1DD.7000101@dannysplace.net>
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On Nov 16, 2008, at 7:15 PM, Danny Carroll wrote: > Eirik =D8verby wrote: >> I have noticed that my 3ware controllers, after updating firmware >> recently, have removed the JBOD option entirely, classifying it as >> something you wouldn't want to do with that kind of hardware =20 >> anyway. I >> believed then, and even more so now, they are correct. > > It kinda depends. If there were a good 8 or 16+ port SATA card out > there that *simply* did SATA with no bells and whistles, then there > would be no point buying a Raid adaptor when you want to use things =20= > like > ZFS. > > But there are no such cards available. Allow me to introduce you to Marvell. The sell the SATA controller =20 used in the Sun thumper (X4500). I've used that same SATA controller =20 under OpenSolaris and FreeBSD. Unfortunately, that controller doesn't =20= use multi-lane cables. When you pack in 3 controllers and 24 disks, =20 it's a cabling disaster. http://freebsd.monkey.org/freebsd-fs/200808/msg00027.html >> Use the RAID-0 disk trick to be able to utilize the controller cache. >> And regarding write-back vs write-through; I believe write-through is >> equvivalent to disabling controller write cache, however it WILL =20 >> cache >> the writes in order to respond to future reads of the data being >> written. I would guess, but I don't know, that this also goes for >> disk-level caches too, though, so it probably doesn't matter. > > It is interesting to me that the default setting on the Areca card was > to have the disk caches turned on. I think that is strange because by > default you have a situation that can lead to data loss even if you =20= > have > a battery backup unit. The Areca cards do NOT have the cache enabled by default. I ordered =20 the optional battery and RAM upgrade for my collection of 1231ML =20 cards. Even with the BBWC, the cache is not enabled by default. I had =20= to go out of my way to enable it, on every single controller. Matt
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