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with Port Multiplication

Posted September 3, 2005, by rob-ART morgan, mad scientist

Many of you have emailed me wondering about the new LaCie SATA II Five Bay RAID Storage System. I've been dying to try it since I heard it has Port Multiplication -- a first in the Mac community.

What's the big deal with Port Multiplication or "PM"? Up to now, the 150MB/s bandwidth of each SATA I data channel has gone to waste since only one 65MB/s drive could be used per channel/port. With the arrival of 300MB/s SATA II, the "waste" was about to get worse. The good news with the PM "aware" host adapter and enclosure is that you can connect multiple drives to a single data channel/port. In other words, in the case of LaCie's S2S, the only thing connecting their 5 bay enclosure to their host adapter is a single eSATA external cable.

But... this could be just a check mark on a feature list if it can't deliver the full 300Mb/s bandwidth to those 5 drives.

LaCie S2S = LaCie's Biggest S2S 5 Disk RAID System Tower with PM support and companion SATA II 3Gb/s PCI-X 4E host adapter
Sonnet = Drive trays removed from LaCie's enclosure and connected to a
Sonnet Tempo-X eSATA 4+4 PCI-X SATA II host adapter
f5 0+1 = firmware based RAID 0+1 using 4 drives plus a "hot spare"
f4 0 = firmware based RAID 0 using 4 drives
s4 0 = software based RAID 0 using 4 drives
s5 0 = software based RAID 0 using 5 drives

The transfer rates of the LaCie S2S in RAID 0 mode were disappointing compared to "conventional" four channel, four drive RAID 0 systems. But that appears to have more to do with the firmware based RAID 0 management than the Port Multiplication scheme. That's because when we defined the drives as JBOD ("Just a Bunch Of Drives) and used Apple's Disk Utility to create a software based RAID 0 set, the S2S speeds jumped up to where we would expect.

Better yet, by using software RAID, we were able to use all 5 drives for a RAID 0 set. (LaCie's S2S RAID management utility will only create a 4 drive RAID 0 set, though this will be changed soon to allow use of all 5.)

Even if you choose to use the firmware based RAID management scheme, there's some good news. You'll find that the speed gap between firmware RAID and software RAID diminishes as the RAID volume fills up. (See the "90% Capacity" graphs above.)

The RAID 0+1 mode, which LaCie calls "SAFE and FAST," may be safe, but it isn't too fast. It stripes two pairs of drives then has those to striped pairs mirror each other. The fifth drive is a "hot spare." The performance might be more acceptable you had 8 drives plus one or two hot spares.

As the title of this article suggests, this report is preliminary. We're continuing to test and learn what LaCie's new SATA II storage system can can and not do. We'll expand this article shortly.

Testing was done with an Apple G5/2.5GHz Power Mac (8GB memory, Raptor 73GB boot drive.) The LaCie SATA II PCI-X card with 4 external ports was installed in the 133Mhz slot 4. (For the record, we also tried it in slot 3 and got the same results.) A BlackMagic Design DeckLink HD was installed in slot 3 when we had the LaCie card in slot 4.

The LaCie S2S RAID Tower has five removable drive trays, internal power supply, and a fairly noisy cooling fan (55 decibels). It can clearly be heard above the fans of the G5 Power Mac. It has one eSATA input port -- remember? Port Multiplication.

Our LaCie S2S box was populated with Western Digital Caviar SE WD2500JS 250GB SATA II drives with 8MB buffer. According to Western Digital, they automatically switch to 3Mb/s mode when a SATA II host adapter is present. WD also ships a WD2500KS with 16MB buffer.

For comparison with a "conventional" one drive per data channel SATA RAID system, we pulled the drives out of the LaCie S2S Tower and ran them "bare," using our custom external 500W power supply, and connecting them to a Sonnet Tempo-X eSATA 4+4 (SATA II) host adapter.

Be sure to move on to our RAID 5 vs RAID 0 vs RAID 0+1 test using the RocketRAID 2220 SATA II PCI-X host adapter and the same 5 drives we used in this article. The LaCie S2S results are included in the RAID 5 article for comparison.

HighPoint will be offering SATA II host adapters with what they call "Infiniband" ports, which are ports/connectors that support up to 4 drives (port multiplication or multi-port). They will be called RocketRAID 2240 and 2224. They will mate with a compatible 4 drive enclosure (X4). We've been assured they are working on Mac drivers for at least the 2224 version.

Blackmagic Decklink 5.0 Utilities
include a Speed Test that predicts performance of a storage system for various kinds of digital video formats. The speed test requires a Blackmagic Designs capture card (DeckLink HD in our case) to be installed to run.

DiskTester is unique drive testing utility that is run using Terminal. It gives you many options to chose. We ran the area test so we could sample various zones on the volume from "empty" to "full" (outer tracks to inner tracks). We specified a 1GB test file, 10% increments, 3 iterations, system cache disabled.

xBench includes a random small block drive test that produces very consistent and credible results.

Finder Duplicate forces the drive or RAID volume to write to and read from itself simultaneously, something that happens in the real world. We use a 1GB TIFF file for the test.


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MacGurus (host adapters, enclosures, bare drives, coolers, hot-swap trays, cables, converters)

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2005 Rob Art Morgan
"BARE facts on Macintosh speed FEATS"
Email , the webmaster and mad scientist