UFS/iSCSI Performance - Good write, lousy read

[dave_the_nerd]

Hello. n00b here, so please use small words.

I built a box last fall - Celeron 1037U, 4GB RAM, 3x 2TB drives in RAID-Z.

I've been getting (and am getting) 60-70MBps transfers, either read or write, (bursts up to 100MBps or so) to any client machine over any NAS protocol I tried. (CIFS, NFS, and AFS.) I'm okay with that performance.

Later on, after checking some threads here, I added an eSATA JBOD (Sil3726 multiplier) enclosure and a Sil3124 card, because I didn't like the thermals in my NAS case. No change in client performance, although ZFS scrubs take longer.

Last fall, I tried creating a file-based iSCSI extent for my Win7 Desktop, which gave me god-awful performance. (Writes were okay, but reads were, like, 5MBps.) At the time, I read a couple forum threads, read how and why ZFS and iSCSI are just crap together, and contented myself with CIFS for a while.

Now, more recently, I added a 3TB HD to the NAS, formatted UFS (not ZFS!) and created another file-based iSCSI extent. I used all the default settings. (512b block, etc.)

AS-SSD Benchmark performance was fine - ~70MBps each way sequential. Write performance was fine - I copied about 1TB of data to it at around 60-70MBps.

But the transfer speed back to the client is still topping out around 5MB/sec. CPU use on the NAS is near-idle. (Except for the ~20% or so that Crashplan is always using.) And it's safe to say that my client machine, network, and HD aren't the bottleneck.

Judging by other posts in the forums, 5MB/sec read from an iSCSI LUN is really bad. So what information do I need in order to identify and address the root cause here? How would I go about getting it?

TIA.

 

[dave_the_nerd]

Oh, and for the record - my intent was to use the LUN as scratch space for torrents and DVD rips. It's not stuff I was keeping or backing up anyway, I just wanted the USB externals off my desk.

I know single points of failure make the sysadmin cry. ;)

 

[dlavigne]

Did you ever locate the bottleneck?

 

[glotzer]

You are using 4gb ram, recommend are at least 8gb and better are 16gb...
RaidZ is NOT recommend, you can easily loss your whole pool on that, use at least RaidZ2.
Did you read ANY of the stickys or the manual?

Id say too few RAM is the problem here ^^

 

[diehard]

You are using 4gb ram, recommend are at least 8gb and better are 16gb...
RaidZ is NOT recommend, you can easily loss your whole pool on that, use at least RaidZ2.
Did you read ANY of the stickys or the manual?

Id say too few RAM is the problem here ^^

They are referring to a UFS volume that they added, not their Raidz... did you read the post?

 

[dave_the_nerd]

Did you ever locate the bottleneck?

The more I poke around, the more I'm thinking it's not the NAS. At least not by itself.

Everything I've found online re: tuning and iSCSI performance is already either set by default or doesn't apply to my situation. And the performance issues are really intermittent. (It's been more than a week since it was last a problem.)

I've been simplifying my network a little bit, found a couple other problems, and I think that may have helped. *fingers crossed*

 

[dave_the_nerd]

You are using 4gb ram, recommend are at least 8gb and better are 16gb...
RaidZ is NOT recommend, you can easily loss your whole pool on that, use at least RaidZ2.
Did you read ANY of the stickys or the manual?

Id say too few RAM is the problem here ^^

FreeNAS detects lower-than-it-would-like RAM and disables the appropriate features. You get a performance hit, but not this big.

If the system were hitting swap, I'd upgrade, but it's not.

If the box eats itself, I'll download it all from Crashplan again.

With only three HDDs, why would I use RAIDZ2?