Tejun Heo wrote:
Yan Seiner wrote:
Sorry for the delayed response. I've installed another controller based
on the SiI 3132 chipset. The esata array is the same; I've simply moved
the esata cables to the new controller. My observations:
1. The JMicron 20360/20363 AHCI Controller (rev 03) controller is far,
far slower. hdparm clocks it at 20 mb/sec and a raid check takes about
15 hours.
Hmm... That's probably due to lack of FIS based switching support.
The hardware (20360/3) can't do it and ahci doesn't support it yet
either. So, only commands to one drive can be in flight at any given
moment which is usually pretty bad for RAID.
So is there hope that FIS switching will make it into the driver or is
this a hardware limitation? I have some time (months if not a year or
two) before I really start to populate my external disk pack. (I have
20 slots with 4 - 5 port multipliers.)
2. The JMicron controller experiences the above errors.
Have you tried forcing the link speed?
Not yet. I spent the weekend building a remote switch and driver for
the esata drive box. (Long story; I need to be able to shut the
external drive pack off via software.)
I need to check the drives as well make sure that the drives are not
jumper-limited to 1.5 gb/sec. (one of those DUH! moments...)
3. The Sil 3132 controller is faster. hdparm says 110 mb/sec and a
raid check takes about 5 hours. This is confirmed by usage - I can
stream 2 videos, record 2 videos, and commercial flag a video in myth
with no visible stuttering. The JMicron controller stutters even with a
single video streaming and recording.
As said above, if you're running RAID on top of it, command based
switching will hurt bad. And 110Mb/s is about the limit of sil3132.
I'm OK with the speed of the sil controller. I'm concerned about the
slow speed of the jmicron controller - it's about 1/3 to 1/5 as fast.
4. The Sil 3132 controller doesn't have any errors even under high load.
Google says the rev 3 version of the JMicron controller has these
issues, and to turn off NCQ on it. It also indicates that these
problems should have been resolved in my kernel - version 2.6.27.4 - but
apparently not. :-(
Nah.. I'm not aware of any such problem and it will work fine w/o PMP.
JMB ahci's are actually pretty good. Lack of FIS switching support
hurts when you use PMP tho.
Is there a way to turn off NCQ on that controller without impacting the
Sil 3132 controller? Any other things to try?
You can do that with libata.force param but if you wanna put parallel
high load to the drives connected through PMP, no matter what you do,
the performance is gonna be bad if FIS switching is not supported.
OK, thanks. I'll check the drive jumpers and see about setting the
lower speed.
The drives are used for storing and streaming videos. The idea is to
have 4 esata channels, eventually with 5 sets of raid-5 arrays. Each
raid-5 array consists of 4 drives, and each drive is on its own esata
controller. The likelihood of multiple raid arrays being used at the
same time is small, so I hope I won't get hit too bad performance-wise.
Even if they get hit, the bandwidth is small; each video stream is about
8gb/hour.
I'm waiting on more hardware (the esata cables, of all things) before I
can test this out fully.
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