July 5, 201016 yr Here is a great deal that made me wish I had a few extra dollars sitting around. Here is an open box 4 bay PMP enclosure for a little over half price: http://www.newegg.com/Product/Product.aspx?Item=N82E16816132029R The usually go for $149. They can be a great way to add another four disks to your Unraid server! Please someone post if you bite on this!
July 7, 201016 yr I think the hard drives on the PMP(Port MultiPlier) are limited to 60MB/s depending on the controller. Command vs FIS based switching. This is a hard ware design situation. Still plenty of fast enough to serve media without interruption.
July 7, 201016 yr Author I kinda think of port multipliers like I think of running 4 drives off a PCI card- terrible Parity Check speeds, but overall acceptable performance.
July 7, 201016 yr I kinda think of port multipliers like I think of running 4 drives off a PCI card- terrible Parity Check speeds, but overall acceptable performance. It's not terrible, it's about 50,000/kbs to 60,000/kbs. I have done tests of simultaneous multiple drive access. Each worked at 60MB/s. That's not too bad. I haven't executed the same test in PCI/33mhz but in PCI/66Mhz i was able to achieve 80MB/s simultaneous access on 2 drives.
July 7, 201016 yr That seems rather unfair, most hard drives will struggle to sustain 60MB/s. unRAID will certainly struggle to sustain 60MB/s when writing. My problems with PMs were unRAID syslogs were noisy due to PMs not being mature technology. Worked OK though. However I didnt like noisy logs because with all the errors you couldnt easily see if there was an issue developing. Three years ago I paid £150 for ten ports and could add another 10 ports for another £70. At the time a similar 8 port RAID card would of been £250. Nowadays probably £120 for ten PM ports vs £75 for 8 real sata ports. For someone struggling to add more ports to an existing unRAID setup, PMs could be the answer.
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