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PostPosted: Fri Aug 17, 2012 11:48 am 
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Setting up a new NASLite-M2 box and so far everything has gone smoothly.

I'm transferring lots of data to it at the moment and one thing I've noticed is that write speeds are very stable (averaging around 36MB/s, with only small variations on throughput even on large copies) until I write to a new drive I've put in the system (a Western Digital Caviar Green (WD30EZRX) 3TB drive, SATA III)

When I write to that disk, transfer starts at a good speed for the first 1GB or so (about 40MB/s) and then the transfer starts "stuttering" -- stalling for a second or two (down as low as a few MB/s), speeding up again for ten seconds or so, stalling again...). Over the course of a large file copy, average speed will gradually decline to about 25MB/s. Not dreadful, but the unstable transfer speed suggests there's a problem.

I thought it might be the fact that it's a SATA III (SATA 6.0 Gb/s) disk, as I had read that some SATA controllers have problems with these drives, so I jumpered the disk to "downgrade it" to SATA II, but that made no difference. I've also tried different SATA controllers (on board and a Silicon Image PCI SATA card) and different network cards, but that made no difference). I also changed the BIOS from AHCI to IDE mode, but again no difference. The system itself is fairly modern, so I doubt it's down to any other system bottleneck.

It's not a huge issue, but if anyone has any suggestions, I'd be grateful.

System: Asus M4A78LT-M LE motherboard (AMD SB710), Sempron 140 processor, 4GB RAM, Intel CT gigabit NIC.


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PostPosted: Fri Aug 17, 2012 6:09 pm 
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EDIT: I originally posted here what I thought was my own solution to the problem, but I was wrong.


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PostPosted: Sun Aug 19, 2012 12:16 am 
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Okay, I've done more work on this and the problem is certainly related to the 3TB disk.

My new box has six disks: 2x 1TB, 2x 1.5TB, and two of the new 3TB disks. When I'm copying to the 1TB or 1.5TB disks, all is well. A constant 35MB/s transfer speed, system load never higher than about 60%.

But when I copy to the 3TB disks, it's a different story. The speed starts high, as I said before, but then the average speed actually constantly reduces over a long period, with regular wild variations in speed. I left a large copy job running overnight to one of the 3TB disks. By this morning, the average speed was down to 8MB/s. And the average load? About 400% Yes, 400%. How does that work?

If you don't believe the number, here's a screengrab:
https://dl.dropbox.com/u/13895942/system-load.png

I'm mystified. Any help appreciated.


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PostPosted: Mon Aug 20, 2012 9:18 pm 
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Location: Up State NY in the USA!!!!
I might look at eh configuration of the drive interface its self. There may be a setting needing to be changed in the firmware to make it work properly. Not sure as I don't have any new, large drives. Sorry I can't be more help.

Mike


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PostPosted: Tue Aug 21, 2012 10:12 am 
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Thanks for pitching in, Mike. I'm not sure what changes I could make to the firmware that would help? As I already mentioned, I jumpered the disk to downgrade it to SATA II, in case that was a factor, although I can't imagine it would be.

The only thing I've ever changed on a disk's firmware is the spin-down time (how long the drive waits before positioning the head in the park position), and that wouldn't be relevant here, but I will have a search and see if there's a newer firmware for the 3TB drives.


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PostPosted: Tue Aug 21, 2012 10:47 am 
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Location: Up State NY in the USA!!!!
It could be an advanced format issue. You might see if there is something to be changed there.

Mike


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PostPosted: Wed Aug 22, 2012 4:44 pm 
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My guess is that the 3TB drive controller is sharing IRQs with the NIC. It may also be caused by the SATA vs SATA2 cable. The speed at the begining is your buffer getting full, followed by a slowdown where the buffer is topped off and waiting on the drive. In any case the problem should be addressed on the hardware level.


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PostPosted: Wed Aug 22, 2012 5:51 pm 
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Thanks for the advice, Tony. When you say address the issue "on the hardware level", would you be able to elaborate slightly? I have moved the NIC to a different slot, tried both PCI and PCI-E NIC cards (both Intel gigabit cards) and moved the 3TB hard drives to different SATA ports, both on-board SATA and using a separate SATA PCI (Silicon Image) controller. None of these options improved matters. What other options would you suggest for hardware "tweaks"?


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PostPosted: Thu Aug 23, 2012 7:53 am 
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What are the drive and controller model numbers? You may be right that the drive is slow, but there has to be a reason. The vallies In the transfer sped sound like the buffer topping off and waiting on the drive. As far as the system load, was the OS done scanning any media? If it was then the high numbers are only due to drive activity, then my guess is high IRQ activity, usually the result of shared IRQ between key components.

What i would suggest is to try and reset the BIOS to defaults, essentially allowing it to reassign IRQs


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PostPosted: Fri May 03, 2013 6:39 pm 
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In case it helps anyone...after putting up with this problem for almost a year, I did one final bit of Googling to try to find a solution. And I did solve it, and perhaps it's something that Naslite needs to address in a future update.

I'm far from an expert in hard disk technology, but apparently the problem I was suffering was caused by misaligned partitions. For Advanced Format disks, default settings in fdisk and parted cause misaligned partitions. Or at least they did in the past. I'm not sure if the issue has been addressed in recent builds of the programs. I'll give reading links at the end of this post.

Sure enough, when I took my two 3TB Advanced Format disks out of my Naslite server and stuck them in a Linux box, gdisk (GPT fdisk) reported a problem with the partitions on my disks. So did parted.

Using gdisk I re-partitioned the two disks, and then re-formatted them.

When I put the disks back in the Naslite machine, transfer speeds were transformed -- I'm now getting a steady 30MB/s or so, compared to an average of 8MB/s or so before I re-partitioned the disks.

I started my reading on this informative thread in a media player forum (not all the posts are helpful, but some of them pointed me in the right direction):
http://goo.gl/K6mN4

A detailed white paper from IBM which includes information on the performance penalties you can suffer with misaligned partitions on Advanced Format disks (although I seemed to suffer far more severe penalties than those suggested in the paper:
http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/

gdisk (GPT fdisk) is a helpful tool: http://www.rodsbooks.com/gdisk/

I used PartedMagic as my Linux LiveCD, it contains all the necessary tools: http://partedmagic.com/

EDIT: One problem that still exists from my original posts (if it is a problem) is that system loads still run at 400-450% when writing to the 3TB disks. This compares to 60% approx when writing to other disks. Why would that happen, and what does it mean?


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PostPosted: Thu May 09, 2013 9:17 am 
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Thanks jdk for keeping us updated. :)


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PostPosted: Thu May 09, 2013 11:11 am 
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Thanks, georg. I was also hoping for a response from the NASLite team. Advanced Format disks are becoming more common. At the moment, based on my findings, you need to partition/format your disks outside of NASLite if you want full performance from your disks on a NASLite box.

I note that NASLite has not been updated in a long time (about 15 months). Yes, on the one hand, if it ain't broke, leave it alone. But if disk partitioning is an issue, then it is a problem that needs to be addressed. Then again, maybe my findings are somehow flawed. Either way, I'm surprised there's been no response.


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PostPosted: Fri May 10, 2013 3:40 pm 
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We'll look into this.

NASLite started using GPT for formatting in v2.62 and M2 in v1.62, to support very large partitions.

Quote:
Thanks, georg. I was also hoping for a response from the NASLite team


Tony asked you JDK, some 9 months ago about your setup to look into this issue, which you never responded.


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PostPosted: Fri May 10, 2013 4:25 pm 
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Ralph wrote:
We'll look into this. NASLite started using GPT for formatting in v2.62 and M2 in v1.62, to support very large partitions.

Thanks for the response. I look forward to your conclusions.

Ralph wrote:
Tony asked you JDK, some 9 months ago about your setup to look into this issue, which you never responded.

I didn't really have anything to add at the time (apart perhaps from saying that IRQs didn't seem to be the issue). In the meantime I updated my NASLite system (now based on a HP Microserver, model NL40), but that didn't solve the Advanced Format disk write issue.

System spec:
Processor: Dual Core 1.5 GHz AMD Turion II
Memory: 3GB PC3-10600 ECC DDR3
Network Controller: Embedded NC107i PCIe Gigabit Ethernet (Broadcom BCM5723) -- I also ran tests using an Intel PCIe Gigbit network card, which did not solve the disk speed issue.


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PostPosted: Sun May 12, 2013 5:47 pm 
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JDK,

Can you post the filesystem details for each of these drives, you'll find this in your NL web stats.

Click on the Hard Drive Icon, then click on each drive link, it will give you some information like :
Please Post the Filesystem Details.

Thanks.

Quote:
General:
This page provides specific information pertaining to Disk-1. Hardware, filesystem and S.M.A.R.T. details are listed below.



Disk-1 Hardware Details:

MODEL: LSI MegaRAID 8888ELP, v.1.20
INTERFACE: DEVICE-SDB, HOST-0, BUS-2, TARGET-1, LUN-0



Filesystem Details:


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