SATA port multiplier support

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Edited by tkaiser at Tue Nov 18, 2014 05:58
cyryllo replied at Tue Nov 18, 2014 05:09
I can't better tranfer between two disk then 25MB/s.

"As expected"

Given the A20's SATA write speed limitation (if you're overclocking it and assign AHCI IRQs to CPU1 you might get near to 45 MByte/sec) and given how ineffectice CBS based switching mode operates especially in your situation where data from one disk is transferred to the other I would suspect that it's not possible to exceed 30 MBytes/sec in such a situation.

Or let's better say it might be funny to play with filesystem and block device tunables (reading/writing as large portions as possible) for this special 'disk to disk' situation. But maybe the circuitry on your multiplier board or the JMB321 itself is generally slow?

As usual: Always test 'from bottom to top'. I would use iozone ("apt-get install iozone3") and measure both disks individually when connected to the PM. And then simultaneously again, one time both disks read, one time both disk write and then one disk read, the other write. Afterwards you have a better understanding whether using the port multiplier will always lead to slow disk access and how CBS based switching affects dual disk access.

I've also ordered one of those cheap JMB321 based boards and will test a bit in december. But my final 'use case' will be different. I won't access different disks connected to the multiplier simultaneously but instead just one at a time for backing up different Macs in a round robin fashion on different 3.5 HDDs in my variant of a BanaNAS (using a dual voltage PSU and different MOSFETs to power the disks individually)

Can some one give me a link (in private message) for proper port multiplier on ebay or aliexpress

Can Anybody Write Step by step Tutorial for Connecting more than one SATA HDD for making BANANA NAS? It would be appreciable and usefull for all the seeking person too

Edited by tkaiser at Tue Dec 9, 2014 12:55
theultimatepras replied at Tue Dec 9, 2014 03:08
Can Anybody Write Step by step Tutorial for Connecting more than one SATA HDD for making BANANA NAS? ...

I ordered one of those cheap JMB321 PMs. When it arrives I will do some tests and add them to

But it's an easy one: don't do RAID with such insane setups since it might be slow as hell and you will loose data

Edited by ExRaspberry at Tue Dec 16, 2014 15:31

Hey guys, I've read this thread carefully, but I still don't know how to get my Banana Pi working with an sata multiplier, and how to "assign AHCI IRQs to CPU1".
I've never before compiled a kernel, so I'm a absolutely beginner at this point.

I'd like to compile the kernel for my sata portmultiplier, which just arrived by today, and I'd like to get as fast transferrates as possible, as I plan to use my Banana Pi as a NAS system, running OpenMediaVault on Bananian as software raid system. I know this will lose speed...but even if I get 10MB/s is is way faster than my old Raspberry Pi, and it benefits of the data security of an raid system ;)

Any advices where to start from?


Edited by tkaiser at Tue Dec 16, 2014 17:00
ExRaspberry replied at Tue Dec 16, 2014 15:29
data security of an raid system

Sorry, but this is plain wrong. RAID is crap with BPi + Port Multiplier. And there's no such thing like 'data security' or 'data safety' when you're talking about RAID. It's about availability. And that's impossible with unreliable hardware setups like the one you're thinking about.

received a JMicron PMP some days ago and it is just working fine with a self-compiled 3.4.104+ kernel and PMP enabled. So far and I know it is not going to be relevant, but I did not even have a single event of failure so far. One thing to mention: in case of multiple disks connected, it is beneficial to use UUIDs - esp. in the uENV.txt in case your root file system resides on one of those disks ;-)

On a single disk (old 2.5 laptop hard disk) I got 20MBytes/s write and 31MBytes/s read over Ethernet using SMB2 protocol connected to a fast Win7 machine.  
I am just building a NAS, based on HP microserver N54L (ECC RAM) and when the disks arrive I may have some time to do some more tests on the BPi.

As a hint to those folks who intend to build a multiple-bay NAS with RAID5 using BPi+PMP. Pls. add all cost for what you need including a solid case and you are getting very close to the HP microserver setup.  

@tkaiser: you mentioned "unreliable hardware" - do you have evidence about bugs / errata sheets and so on ? Is there a compilation of such information?

Edited by ExRaspberry at Wed Dec 17, 2014 19:09

WHy shouldn't RAID1 work? Sure it's not as fast as on native raid controllers or on systems with multiple sATA ports. But in general this should work with OpenMediaVault.
Correct me if I'm wrong, but OpenMediaVault lets yo choose which discs to use for an RAID. If a PMP works well with my Banana Pi OMV should be able to use it as RAID.

I'm going to move all my personal data and videoclips from my internal PC HDD to the Banana Pi - and that's why I wanted to create a RAID1. All my personal data might get inrecoverable lost if there's no backup. Writing on OMV Banana Pi discs might be slow...but reading should be fast as there would be no RAID system, shouldn't it?

@BPiuser: Where do I get the informations about compiling a PMP enabled kernel?
And did you "assign AHCI IRQs to CPU1"? Does this need to be changed for the new kernel or in a config file?

@ExRaspberry: I followed this thread ... ... ly_on_bananian.html

Edited by tkaiser at Sat Dec 20, 2014 04:04

Regarding RAID-1 and 'reliability' simply read f4exb's experiences here:

Doing RAID on such an unreliable hardware is just insane.

The aforementioned N54L with FreeNAS/ZFS/raidz2 is a far better approach, will be ten times faster at nearly the same cost and will provide a NAS solution that is able to provide data integrity, availability and safety (the latter when combined with ZFS snapshots and a second sync location where you transfer the snapshots incrementally via 'zfs send/receive')

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