Ultra Slow Read Performance

[technologiq]

This is my second unraid build.  My previous build was using the free version of unraid with a P4 and 2GB RAM with some old hard drives.

 

This time I'm using a Q6600 w/ 4GB RAM w/ Unraid 5.0rc16 Plus.    I have a Boxee Box I stream to and it worked great on my old box but this time it's totally struggling to do push the video (unwatchable).

 

I do have a parity and a cache drive which I thought would help things, not hinder them.

 

I've enabled jumbo frames, I'm connected va gigabit ethernet.  Any ideas?

syslog.txt

[garycase]

Two thoughts ...

 

=>  First, use the final release (v5.0)

 

=>  Second, reset to standard Ethernet, just to be sure you haven't got the parameters set in a manner that's causing this issue.

 

Note that both parity and cache should have NO impact on read performance of the array.

 

[garycase]

... an additional thought=> check to be sure you've got AHCI enabled for the SATA mode.  You shouldn't have any issue with streaming even if it's not; but this will ensure that you're using the disks in the most efficient manner.

 

[technologiq]

Sigh - I didn't realize the 5.0 stable was listed on that page.    Thank you.  You also answered my question about performance being affected by parity - thank you.

 

I'm going to install 5.0 stable and reset my ethernet.

 

 

[garycase]

Parity should not have an impact on read speeds UNLESS you're reading from a failed disk (a "red balled" disk that shows as Disabled on the Web GUI) => in that case, the system has to read all of the OTHER disks (everything except the bad disk) and recreate the data for the failed disk.

 

But as long as the disks are okay, parity has NO impact on read speeds.

 

Clearly a parity disk has a major impact on writes -- as you now have to do 4 disk operations for every write (2 reads, 2 writes).    A cache disk eliminates that impact for all cached shares, as the writes are actually done to the cache disk, and the data is transferred to the parity-protected array later.