Interesting HDD performance issue N40L...... Please have a look....

[andyclimb]

Recently purchased an HP N40L to set up for a NAS, installed 8GB RAM, and a Startech 4 port PCIeX4 SATA III controller card. I have used the most recent BIOS-mod to open all the bios features (I didn't use the russian one, but the one from here http://homeservershow.com/forums/in...for-microserver-n40l-enables-hidden-features/

I have a random collection of HDD drives lying around and have decided to put them together to see what happens. They are listed below:

SIZE type SATA MAN MODEL

2TB HDD 300 Samsung HD204UI
1.5TB HDD 300 Seagate ST31500341AS
1TB HDD 300 Samsung HD103UJ
1TB HDD 300 Samsung HD103UJ
250GB HDD 300 Seagate ST3250318AS
250GB HDD 150 Seagate ST3250310AS
60GB SSD 600 Crucial CT064M4SSD2
120GB SSD 600 OCZ AGT3-25SAT3-120G

Initially I have the first 4 drives occupying the four drive bays on the N40L, but I was getting aweful speeds. When i tested each drive separately I identified the two 1TB, SATA II drives, as having write speeds of ONLY 14MB/s, which is VERY SLOW. They still had read speeds of >100MB/s, but just slow write. Only these two drive are affected. In fact the older SATA I, 250GB HDD has read and write of over 70 MB/s and all the other HDD have read and write of over >100 MB/s as expected. unplugging the other drives does not change things. changing the drive bays around does not change things. plugging one of them into the 5th port designed for the disk drive does not change anything, however, any one of the other drives will easily read/write >100MB/s in this same slot.

I refused to believe that BOTH drive could have the same problem as I have two. So i plugged them into the eSATA port in the HP machine, via one of these HDD dock devices, and MAGIC, suddenly both 1TB drives that only wrote at 14MB/s now read and write at >100MB/s. The same is true if I plug them both into the SATA PCI controller card.

WHAT on each is causing this?
Why is it JUST these two drives that fail to work, correctly, but the others including older SATA I drives are not affected.

I have tried adjusting the settings in the bios for IDE, legacy IDE, AHCI, and power management but to no avail.

This is the command I was using to write/read

dd if=/dev/zero of=/mnt/hdd/ddfile bs=2048k count=10000
dd if=/mnt/hdd/ddfile of=/dev/zero bs=2048k count=10000

which gives a 20GB file.

ANY ideas would be appreciated?

Thanks for having a look if you got this far!

Andrew

 

[mav@]

Check that drive write caches are enabled. On very alike in hardware HighPoint RAID controllers BIOS disables write caches, that significantly reduces single-stream write performance. FreeBSD after some point got cache control support via kern.cam.ada.write_cache tunable.

 

[cyberjock]

Someone else in the forum had a problem with some supermicro enclosures. Supermicro's manual and website said they were "SATA" but did not specify what speed. The first generation of those enclosures were from back in 2005/2006 so sata2 didn't exist yet. You may be having an issue with your enclosure not being able to negotiate the speeds correctly. You may be in a situation where your SATA3 controller is trying to negotiate a connection with your SATA2 hard drive over a SATA1 compatible enclosure.

If you can force a slower speed for the controller I'd try that first.

If not, you can force your Samsung drives to SATA1 speeds by a jumper setting described at http://www.techarp.com/showarticle.aspx?artno=651&pgno=3. If that fixes your write speeds I'd recommend forcing all of your drives to SATA1 just to ensure you don't later have these communication issues with other drives because of whatever is going wrong. Your hard disks are likely not being bottlenecked at SATA1 speeds in your zpool, so you won't see a performance penalty by forcing SATA1 for all drives.

I know a few people that always force SATA1 speeds on RAID arrays just because the signal is less likely to be distorted by EMI.

Obviously this all just ideas and I may not be on the right path but it's something to try :P

 

[andyclimb]

Hi,

thanks for the feedback. I've currently got the drives hooked up via an PCIe SATA card, running at full speed. I'm experimenting with hypervisor.

I shall test the jumper issue, but first I need to find some jumpers. Hard than you think these days!

I will also test write caching, as i know that is it disabled in the bios!

It is weird as its a brand new HP N40L, so it should not be anything related to the enclosure.

 

[mav@]

If there is no jumpers, you can try to limit speed from the controller side. ahci(4) driver allows to do it via hint.ahcich.X.sata_rev tunables.

I've seen early 6Gbps Marvell chips negotiating 1.5Gbps with 3Gbps drives. Limiting speed to 3Gbps forcefully from controller side helped in that case. I can suppose other negotiation problems there.

 

[andyclimb]

That is wierd, I swear I wrote a reply to this post a few days ago.

Solve the problem. Enabled write caching in the BIOS. immediately fixed the problem. no idea how, or why it only affected these two drives when connected via the on-board SAS. who knows...

jumper settings made no difference, although i did discover the slower 250Gb drive was actually restricted, so now it runs at SATA 300.

Thanks for the help...

I've just posted an another question RE rsync... causing me a head ache...

A