Why only 25 MB/s SATA2 to SATA2?

[Peroxyde]

Hi,

On a motherboard having only SATA2 connectors. I hookup two drives, 1.5TB WD Black and 4TB Seagate ST4000DM000 (the recent 5900 rpm, HDD.15).

I copy the content of the 1.5TB drive on the 4TB drive. The progression dialog show that the transfer speed average around 25 MB/s. While I don't expect it to saturate to the max bandwidth of SATA2 (3 Gb/s). But 25 MB/s is pretty slow for 2 hard drives which are directly connected to the same motherboard.

Is there anything I can do to increase the transfer rate between these 2 disk? Thanks in advance for any advice.

 

[dave_the_nerd]

What kind of files? 1,000,000 1MB files will transfer slower than 1,000 1GB files.

Storage controller drivers should be updated. AHCI mode?

Memory or caching may be an issue. What else is the computer doing? Is one of these a boot drive?

 

[Peroxyde]

What kind of files? 1,000,000 1MB files will transfer slower than 1,000 1GB files.

Files are rather big (MP3, video, ISO, VM images). Overall less than 10,000 files. The 4TB disk is formatted NTFS, unit size = 64K.

Storage controller drivers should be updated. AHCI mode?

I believe it is set to AHCI mode in the BIOS. Cannot check right now in the middle of the file copy. I am using Linux, lshw reports "driver=ahci latency=0 maxlatency=1 mingnt=3"

Memory or caching may be an issue. What else is the computer doing? Is one of these a boot drive?

The computer is mostly idle. The 2 drives in question are pure data drive. The OS is Xubuntu 13.04 on a separate 500GB drive. The computer has 8GB RAM.

 

[dave_the_nerd]

Huh.

Is it possible the files are highly fragmented?

Otherwise, I'd be suspicious of an NTFS formatted drive on a Linux system. The NTFS drivers for linux have historically not been very good. (Although I haven't tried using/benchmarking any recently, so I'll happily admit my info is probably out of date.)

 

[XavierMace]

Or it could be a poor quality controller. I've got an ECS board with the shittiest RAID "controller" on the planet.

 

[Eeqmcsq]

Since you're on Linux, try copying some of the files from your 1.5TB drive to /dev/shm to see what kind of read speeds you get. Then try copying those files from /dev/shm to your 4TB drive to see what kind of write speeds you get. If you have 8 GB of physical RAM, your /dev/shm should be about 4GB by default.

Also, can you tell us the motherboard model number? Maybe those two SATA ports are on some kind of a SATA port multiplier, and perhaps there's some sort of a simultaneous read/write contention going on?

 

[Peroxyde]

Since you're on Linux, try copying some of the files from your 1.5TB drive to /dev/shm to see what kind of read speeds you get. Then try copying those files from /dev/shm to your 4TB drive to see what kind of write speeds you get. If you have 8 GB of physical RAM, your /dev/shm should be about 4GB by default.

Also, can you tell us the motherboard model number? Maybe those two SATA ports are on some kind of a SATA port multiplier, and perhaps there's some sort of a simultaneous read/write contention going on?

Hi,

This is a really good idea. Thank you.

- Motherboard: Asus P5N7A-VM (bought in Aug 2008) http://www.asus.com/Motherboards/P5N7AVM/#specifications

- 1.5 TB Disk : WD Black WD1501FASS
- 4 TB Disk: Seagate ST4000DM000

SATA Mode in BIOS was set to "Sata Mode" I have now changed it to "AHCI". The sustained transfer speed from 1.5TB to 4TB increases from 25MB/s to 35MB/s (+40%).

Copying a single 3.5 GB File :
1.5TB (AHCI Mode) -> /dev/shm: 135 MB/s
dev/shm -> 4TB (AHCI Mode)...: 32 MB/s 

Copying 150GB (mostly VM images, file size from 5GB to 30GB)
1.5TB -> 4TB (SATA Mode): 25 MB/s
1.5TB -> 4TB (AHCI Mode): 35 MB/s

Thanks to the test writing on the RAM disk, it looks like that the write speed is the limiting factor. For that backup, I had a lazy choice of doing it over a 100Mb/s network or using a USB2 enclosure. Finally I went for SATA to SATA hoping for a "much faster speed improvement" something like 10x faster. It's faster indeed but only by 2x to 3x compared to USB2.

Well it was an interesting experiment. Fortunately I don't have to do this often. It take quite almost half a day to transfer 1.5 TB.

 

[Eeqmcsq]

At least you've isolated the bottleneck to writing to the 4TB drive.

Even still, 35MB/s is too low for the 4TB drive. I poked around for a review:

http://www.rwlabs.com/article.php?cat=&id=810&pagenumber=5

and the writes should be somewhere between 50 MB/s and 170 MB/s.

But if you don't do this very often, and if you're ok that at least it "works", then, oh well!

 

[XavierMace]

Yeah, I would chalk up the rest of the missing performance to the crappy SATA controller.

Out of curiosity, what ports do you have the drives plugged into?

 

[thecoolnessrune]

I don't see any tests of your writing to the 1.5TB drive.

NTFS drivers in Linux aren't great as other posters have said. I wouldn't be surprised if your problem is the NTFS write speeds in Linux tank, and it looks like the 4TB drive is the issue because that's the only one you've used for writes.

If you want to see what I'm saying, take a look at any review (for instance on smallnetbuilder) at small NAS Routers that can support external hard drives. These are almost always built on small Linux based systems. If you look at the graphs, you'll find the difference between ext4 (Linux built in support) and NTFS write speeds are immense.

You can see an older article espousing the performance of ext4 on Linux here.

 

[Cerb]

Files are rather big (MP3, video, ISO, VM images). Overall less than 10,000 files. The 4TB disk is formatted NTFS, unit size = 64K.

64KB? That could have some negative effects. NTFS supports many sizes, but there's generally no advantage to larger than 4KB. The same holds true for most Linux FSes, too.

Try making sure, as well, that the drives are mounted async. Unofrtunately, checking this is something I'm not 100% on. I've had the situation where one distro wouldn't mount if I set it (unsupported option), but another (an Ubuntu) mounted HDDs sync unless told otherwise. The thing is, I couldn't really tell except by watching IOtop (one of several rough edges I wish they'd deal with). An HDD supporting hot-plugging might get mounted that way, and that will cut speeds by more than half, typically (flush is the ideal hot-plug option, which is similar to what Windows does, by default).

I use NTFS under Linux all the time, and aside from the necessary higher CPU time due to FUSE, it works fine for me, only transferring a little bit slower than Windows would.

 

[Lorne]

Swap the SATA cables and see if there is a difference.

 

[tweakboy]

Well, like the gurus said, drive could be really fragmented. Also large files compressed files will be slow 35 to 40mbps is about right.

If its a bunch of files at 500mb per file it would be much faster then 1GB per file. gl

 

[XavierMace]

Guy's keep in mind he's talking about an nForce based controller (which weren't great to begin with) running under Linux (who's driver support I would guess isn't great). That's not exactly a high performance setup.

 

[Peroxyde]

I don't see any tests of your writing to the 1.5TB drive.

NTFS drivers in Linux aren't great as other posters have said. I wouldn't be surprised if your problem is the NTFS write speeds in Linux tank, and it looks like the 4TB drive is the issue because that's the only one you've used for writes.

Thanks gentlemen. Following your latest inputs has helped to narrow down the cause. It is likely NTFS under linux which is the main cause of the low write speed. Here is some new more acceptable speed when writing directly to ext4. Stupid of me I didn't think about this earlier:

3.5 GB from Ram drive to 1.5TB (file system = ext4, WD Black WD1501FASS): 200 MB/s
3.5 GB from Ram drive to 0.5TB (file system = ext4, Seagate ST3500320AS): 180 MB/s
50 GB from 0.5TB to 1.5TB (both ext4 File System): 80MB/s in average

Based on this test, I think the SATA cables and the SATA controler of the nForce 730i / GeForce 9300 should be acceptable for my modest needs.

The reason the 4TB drive has NTFS is b/c I put it in the Hyper-V 2012 server which I use for my exercises. As this server is on all the time, I just add that 4TB drive, create a shared folder and use it as backup drive. I hope nothing will break for a few months. I plan on building a NAS Server. At that time, I will repurpose the 4TB drive correctly.