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Author Topic: SATA Port Multiplier throughput.  (Read 2362 times)
dk
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« on: May 24, 2010, 10:11:55 AM »

I was wondering if anyone tested a SATA Port Multiplier on a plug computer and got reasonable throughput of at least 200MB/s.

I have a sil3726 based port multiplier (an Addonics AD5SAPM) and was expecting to max out the SATA port (at least 220MB/s). But this was a big disappointment, because the combined speed of 4 disks only got me about 134MB/s. The individual disks can get 90MB/s while attached to the PM.
Searching around I see more postings indicating that this is the maximum speed of the sil3726 in some cases, so if anyone tested a plug computer with another port multiplier, please post your throughput.
(for example: http://www.mail-archive.com/linux-ide@vger.kernel.org/msg09931.html)
Why I was expecting a least 220MB/s, see this review (external review, but now hosted on Addonics own site):
http://www.addonics.com/news/media/2006/amug_portmultiplier.pdf


To get the throughput:
assuming the drives are mapped at /dev/sd{a-d}, performing a dd from the disks of 512MB. Command:
    for i in a b c d ; do { sudo ionice -c 1 dd if=/dev/sd$i of=/dev/null bs=512k count=1k & } ; done
reports four times:
1024+0 records in
1024+0 records out
536870912 bytes (537 MB) copied, 16.005 s, 33.5 MB/s
Total: 4*33.5 = 134MB/s
« Last Edit: May 24, 2010, 10:35:36 AM by dk » Logged

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