Hi folks,

I have a smale problem with my cache disk and need some help:

I changed my chache disk today from a 2.5" wd black to a 240GB SSD.

Now, the write speed is very slow - about 19MB.

With the wd black, i had 65MB.

My question now, are there some parameters to adjust for the chache drive or

Are there some other hints to improve the write speed?

I did some tests with hdparm and it shows me a rate of 285MB.

 

EDIT: I did several reboots and now, the write speed is back to 60MB/s - strange 

 

Thanks for your help

Zoni

That's the speed of no cache drive at all .

No wonder you're annoyed!

 

Not to add to the annoyance, but you've double checked your settings?

a. The cache drive really is defined as a cache drive and not just another data drive?

b. The share you're writing to, is setup to use the cache drive?

c. When you access the physical cache drive (for example from the Web Gui, by clicking on the little folder icons to see the actual files and folders),

then you can see that your spanking new SSD cache actually has the data? ...thus double checking that somehow unRAID isn't just writing straight to the data disks?

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edit: DOH! Glad things are up to speed. I don't have an SSD, but my uninformed comment is "that sounds slower than I'd expect." What's the constraint? Is it the network or the SSD's write speed?

a) yup

b) yup

c) yupyup 

 

I know all these things and i checked it directly after installing the new SSD - but i did no reboot.

My Sys has also more the 4GB RAM (8GB) - maybe this is the problem.

But it should be fixt in v5.0.4 what i use 

 

Its a little bit slower during File transfere, yes - but the target was to speed up PlexWeb and the interface on the clients.

And this is massively faster then before 

 

Thanks for your reply

 

EDIT: It seems that unraid itself limits the transfere - now i have 65MB/s constantly. The Network can handle up to 90MB/s.

 

It seems that unraid itself limits the transfere - now i have 65MB/s constantly. The Network can handle up to 90MB/s.

 

There is no built in software limit for UnRaid transfer speeds that I am aware of. I get consistent speeds of 80-110MB/s when transferring to my SSD cache drive from a networked PC.

 

Ok - then its a limit of the Realtek 8111E on the Mainboard maybe (Asrock B75 Pro3-M)

But the funny thing is, i can read with almost 90MB/s from the unraid.

Just the write-speed seems limited to 65MB/s.

One thing I would look at is the governor on your cpu. If it is set to conservative or ondemand, it may not be speeding up for the transfers and will definitely affect your transfer speeds in a negative fashion....

 

This wil show you what it is currently set at

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
cat /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor

 

This will set it to performance

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo performance > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor

 

Note: If your cpu is dual core, obviously remove the last two lines

 

If you see a difference, that is probably your problem. I would recommend setting it back to ondemand, but play around with the sampling_down_factor and up_threshold (Google these forums. You'll find lots of posts)

 

Here's a link to an old post I made discussing when I first came across the issue: http://lime-technology.com/forum/index.php?topic=22633.0

 

 

Is this a console-commando?

I get the output "no such file or directory"

It is a console command. I run it through putty. What are your system specs (Hardware and unRaid)

Ah ok - did it over putty too - but got this message 

Using unRAID 5.0.4, i3-2100T and a Asrock B75 Pro3-M with 8GB RAM (NIC RTL8111E)

You may have it disabled in your bios. I believe it's called "Speedstep" for Intel-based systems...

Note: I Just noticed that Tom changed the cpu scaling drivers from built in to modules starting in 5.0.1, so you may need to modprobe them to get them to work.

 

For 5.0.1, changed the cpu frequency scaling drivers from "built-in" to "modules" - this will at least let you manually remove/install these drivers if desired.  Also added a couple more; the complete list is:

 

drivers/cpufreq/acpi-cpufreq.o

drivers/cpufreq/mperf.o

drivers/cpufreq/powernow-k8.o

drivers/cpufreq/pcc-cpufreq.o

drivers/cpufreq/powernow-k6.o

drivers/cpufreq/powernow-k7.o

drivers/cpufreq/speedstep-ich.o

drivers/cpufreq/speedstep-lib.o

drivers/cpufreq/speedstep-smi.o

drivers/cpufreq/p4-clockmod.o

drivers/cpufreq/cpufreq-nforce2.o

 

 

Try this to enable the module:

modprobe acpi-cpufreq

 

and then try the other code again.

 

Hmmmm.... thanks for the hint - i got this error when i type "modeprobe acpi-cpufreq":

 

FATAL: Error inserting acpi_cpufreq (/lib/modules/3.9.11p-unRAID/kernel/drivers/cpufreq/acpi-cpufreq.ko): Device or resource busy

 

But i found out, that the i3-2100T is working between 1600MHz and 2500MHz.

I am not shure, if this can affect the transfere over the NIC - 1600MHz sounds enough for full speed on the LAN-NIC.

 

 

Hmmmm.... thanks for the hint - i got this error when i type "modeprobe acpi-cpufreq":

 

FATAL: Error inserting acpi_cpufreq (/lib/modules/3.9.11p-unRAID/kernel/drivers/cpufreq/acpi-cpufreq.ko): Device or resource busy

 

But i found out, that the i3-2100T is working between 1600MHz and 2500MHz.

I am not shure, if this can affect the transfere over the NIC - 1600MHz sounds enough for full speed on the LAN-NIC.

 

Based on the error you received, I'm assuming the typo in "modeprobe acpi-cpufreq" was a transcription error in this reply, right? (It should be modprobe).

 

Well, to be honest, my issues were happening when my cpu was running @ 800mhz. If 1600mhz is your minimum, chances are good that it is not the root of your problem. Though I would still be interested to know why you can't access the governor settings of your chip...

I was looking around on some other site, and noticed a comment someone made about their SSD being Slow on writes.

They were running Windows 7.  I quote their solution,

simply go into the Device Manager and disable "Write caching" on the "Policies" tab for your SSD.

Your mileage may vary.

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Zounds!

After posting the above, I found this link:

http://www.speedguide.net/articles/ssd-speed-tweaks-3319

Most of the article is about Windows tweaks, but in the section called, "SSD Partition Alignment" are some tweaks for "Under Linux".

The article is from 2010. Is the Partition Alignment step still needed/desirable for unRAID?

hi folks,

i did some additional tests.

I implemented an empty HDD on my computer for transfering files to the unraid cache ssd.

The constant write speed is now 93MB.

It seems, the 65MB-limit was the HDD on my PC. Peak transfere to the ssd was at 119(!) MB/s.

So unraid has implemented the cache-ssd properly 

The only strange thing were the few reboots i needed till the write-speed on the ssd was working.

 

Thanks to all of you for your quick help

 

EDIT: Mad a test with an Intel PCIe NIC and copied a file from my Intel SSD 330 to the Crucial M500 cache-SSD >> constant throughput: 104MB/sec.  (Hell fast)

The Cache-SSD is working 

Excellent news!