3037 Views 5 Replies Latest reply: Feb 26, 2009 1:53 PM by DSA1
If you want to use PM, both the card and enclosure must support it. The card has to be able to handle multiple drives on one SATA cable and he enclosure needs the circuitry to connect multiple drives to one SATA connector. Note that PM enclosures can have up to five drives but the total transfer rate is limited to 3 Gbits/second (about 300 MBytes/second). With newer drives capable of 120 MBytes/second each, a PM enclosure can be slower than one with a separate SATA connection for each drive. That doesn't necessarily mean more cables, since some SATA cards and enclosures use iPass cables which handle four SATA drives per connector.
There are also multiple drive enclosures with built-in RAID controllers that can connect to a non-PM SATA card or one of the spare SATA port on the Mac Pro logic board. The total data trasfer rate ill be limited by the single SATA connection to the same speed as with PM.
Anyone forseeing multiple bay enclosures could initially go with a nonPM card?
Most users decide to go with port multiplication "PM" as it is relatively inexpensive, reduces cable clutter (by using a single SATA cable) and can provide high performance. The SeriTek/5PM is the best 5-bay PM enclosure that I have tested based on quality, cooling and quiet operation. Using a PM enclosure requires the use of a SATA host adapter that also supports PM. You cannot use a non-PM controller with a PM enclosure as it will not be able to see all of the hard disks.
The SeriTek/5PM can provide RAID performance as high as 240MB/sec and maintain a high level of performance even as the hard disks approach 90% full. Mac Pro compatible controllers that are a good choice for high performance configurations with the SeriTek/5PM include the Sonnet Tempo E4P which uses Disk Utility to create RAID sets and the HighPoint RR2314 which uses the HighPoint web manager to support RAID 0, 1, 5, 10, 50 and JBOD configurations.
Using a direct connect 4/8 bay configuration (each hard disk as its own channel) can provide higher performance when the volume is empty. However, this setup is usually significantly more expensive. An 8-16 channel controller usually costs $500 to $1000 plus dual 4-bay enclosures can be another $400-500 each. Larger enclosures will be more. You can easily spend $1400-$2000 and still need to purchase hard disks.
When you compare the cost of direct connect systems to the SeriTek/5PM matched with a Sonnet Tempo E4P or the HighPoint RR2314 you start to see the considerable price difference. The SeriTek/5PM with the E4P or RR2314 provides a high quality, quiet enclosure that keeps the hard disks cool for $700-$800. 200MB/sec performance is more than enough for most users. If not, the beauty of the SeriTek/5PM and these cards is that you can connect an additional SeriTek/5PM to the existing card if you want 400MB.sec. performance. This can be done with up to four SeriTek/5PM enclosures which provides performance as high as 700MB/sec.
While non-PM enclosures and cards certainly exist they are usually a more expensive option. You will need to decide which option is best for your particular needs.