Date: Tue, 07 Jun 2011 11:35:49 +0300 From: Alexander Motin <mav@FreeBSD.org> To: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: PCIe SATA HBA for ZFS on -STABLE Message-ID: <4DEDE2E5.6080406@FreeBSD.org> In-Reply-To: <mailpost.1307421239.2786523.71162.mailing.freebsd.stable@FreeBSD.cs.nctu.edu.tw> References: <mailpost.1307421239.2786523.71162.mailing.freebsd.stable@FreeBSD.cs.nctu.edu.tw>
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On 07.06.2011 05:33, Matthew Dillon wrote: > The absolute cheapest solution is to buy a Sil-3132 PCIe card > (providing 2 E-SATA ports), and then connect an external port multiplier > to each port. External port multiplier enclosures typically support > 5 drives each so that would give you your 10 drives. > > Even the 3132 is a piss-ant little card it does support FIS-Based > switching so performance will be very good... it will just be limited > to SATA-II speeds is all. SiI3132 is indeed good for it's price and it is quite good for random I/O. But at burst speeds it is limited lower then SATA-II. Even lower then PCIe 1.0 x1 it uses. IIRC I've seen about 150MB/s from one port and about 170MB/s from two. If burst rate is important, SiI3124 chip is much better -- up to about 900MB/s measured from 4 ports. The only issue is PCI-X interface: either motherboard with PCI-X needed, or card with PCIe x8 bridge (like these http://www.addonics.com/products/host_controller/adsa3gpx8-4e.asp), but last case is too expensive. There are also much cheaper (~$50) PCIe x1 bridge SiI3124 cards (http://www.sybausa.com/productInfo.php?iid=537). They are not so fast -- about 200MB/s, but still more then SiI3132. And they still have 4 SATA ports. > For SSDs you want to directly connect the SSD to a mobo SATA port and > then either mount the SSD in the case or mount it in a hot-swap gadget > that you can screw into a PCI slot (it doesn't actually use the PCI > connector, just the slot). A SATA-III port with a SATA-III SSD really > shines here and 400-500 MBytes/sec random read performance from a single > SSD is possible, but it isn't an absolute requirement. A SATA-II port > will still work fine as long as you don't mind maxing out the bandwidth > at 250 MBytes/sec. Agree. Intel on-board ports rock! Recently I've built new system with two OCZ Vertex 3 SSDs connected to 6Gbps SATA ports on Intel Sandy Bridge class motherboard. UFS on top of graid RAID0 volume gives me about 950MB/s on both read and write! > To get robust hot-swap enclosures you either need to go with SAS or you > need to go with discrete SATA ports (no port multiplication), and the > ports have to support hot-swap. The best hot-swap support for an AHCI > port is if the AHCI chipset supports cold-presence-detect (CPD), and > again Mobo AHCI chipsets usually don't. Hot-swap is a bit hit or miss > without CPD because power savings modes can effectively prevent hot-swap > detect from working properly. Drive disconnects will always be detected > but drive connects might not be. I would say it depends. In some cases it is easier to detect hot-plug then hot-unplug, as device sends COMINIT that should wake up port even from power-save state. With ICH10, for example, I've managed to make both hot plug and unplug work even with power-management enabled: hot-plug via tracking COMINIT, unplug via it's CPD capability. Without PM it "just works". :) -- Alexander Motin
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