NAS: DS213+ & WD20NPVT – 3. Performance and Encryption

As announced in the first and second post about Synology DS213+ and the Western Digital WD20NPVT, this post is about the effective data rates achieved by the NAS and the hard drives. It contains the data rates measured when reading files from the DS213+ (download), as well as the ones measured when writing to it (upload) for both unencrypted and encrypted folders on the NAS. For measurement both one large file (1 x 50GB) as well as many small files (100,000 x 10KB) have been transfered to/from the NAS.

Measured Values

The following tables compare the measured data rates to the ones published by Synology.

Large file

Note that for the measurement in this post a 50GB file was used, whereas Synology transfered a 5GB file, which should not make much of a difference.

Operation Data rate (measured) Data rate (Synology)
Upload 51.87 MB/s 84.31 MB/s
Upload (encrypted) 21.32 MB/s 24.65 MB/s
Download 40.89 MB/s 110.36 MB/s
Download (encrypted) 37.21 MB/s 49.58 MB/s
Client (internal) 111.55MB/s

Small files

Note that for the measurement in this post a 100,000 10KB files were used, whereas Synology transfered 1,000 5MB files. So the rates here cannot really be compared, as transferring more smaller files results in a bigger overhead and therefore in a lower transfer rate.

Still, it is remarkable, that Synology only measured the performance when transferring small files to unencrypted folders. Maybe the data rates measured for encrypted folders didn’t look too good?

Operation Data rate (measured) Data rate (Synology)
Upload 0.44 MB/s 43.82MB/s
Upload (encrypted) 0.05 MB/s
Download 0.75 MB/s 58.15MB/s
Download (encrypted) 0.49 MB/s
Client (internal) 4.52MB/s

Measurement

All data rates have been measured from the same client PC using Microsoft Robocopy, connecting to the NAS via SMB protocol.

The Client and the NAS are connected via a Linksys SE2800 switch, using Gigabit Ethernet.

The following table lists the NAS details, as well as the client PCs’ used for measurement in this post. In addition, the details of the client PC used by Synology are listed in the table.

Synology DS213+ Client PC Client PC (Synology)
OS DSM 4.1-2657 Windows 8×64 Windows 7
CPU Freescale MPC8544E 2x 1.067GHz Intel T7250 2×2.0GHz Intel Core i5 750 2.67GHz
RAM 512MB DDR3 4GB DDRII (2x2GB at 667MHz) 4GB DDRIII
SSD/HDD Western Digital Green WD20NPVT x2, RAID 1 Samsung 840 Pro (256GB) SVP200S3 (60GB) SSD x 2, RAID 0

Conclusion / Differences

There obviously are differences between the values measured here and the ones published by Synology. What are the reasons for this?

For the small files, the main reason for the difference surely is the smaller size of the files copied, as mentioned above. Why did I choose this smaller size and bigger number? It was not my main objective to compare the values to the ones measured by Synology. However, I was interested at what rate small files are actually copied. For me, small files are less than 1MB. Have you ever tried to copy a directory with a large quantity of small files (several KB each) such as an eclipse workspace or an SVN repo? It takes ages. I never thought, though, that they are copied with a data rate of less than a MB per sec.

For the large file I presume the difference between the measured values and the ones by Synology can be found in the differences in measurement set up. Synology used a faster CPU, fast RAM, an Raid 0 and direct connection between client PC and NAS.

Moreover, I don’t know what software and protocol Synology used for transfer. Maybe they used FTP, which might perform better than SMB. In addition, it might be even faster for small files, because they can be transfered using several concurrent connections and not sequentially, as it is done by robocopy.

Anyway, Synology’s download rate of 110 MB/s somehow still is a miracle to me, as this is almost as fast as when I write to my local SSD with robocopy…

Finally, I must say that it is astonishing why uploading (that is writing) large file is faster than downloading (for unencrypted files). I repeated measurement of all four large file operations several times but I got nearly the same results every time (± 1 MB/s). This seems to have something to do with Robocopy or SMB, because downloading the exact same file via FTP (Filezilla) yields a data rate of about 65 MB/s.

Maybe I should write another post comparing FTP and SMB, when I have time 🙂

NAS: DS213+ & WD20NPVT – 2. Power Consumption

As announced in the first post about the Synology DS213+ and the Western Digital WD20NPVT, here’s the measured power consumption of the NAS and the two hard disks in differnt operational modes.

Measured values

The following table compares the values measured to the values as specified in DS213+’s specification.

Operational Mode Mean power consumption (measured) Power consumption (specification)
Off ~1W
System hibernation 2.9W 2.64W
on – HDD hibernation 9.6W 10.08W
on – idle 12.56W
on – download 13.94W 22.20W (“access”)
on – upload 15.47W 22.20W (“access”)

The spec mentions higher values for “access” and, HDD hibernation probably because they used 3.5″ HDDs. However, the value for hibernation is lower. Maybe that’s due to the measurement accuracy.

Note: The power consumed by the power supply when the device is off, is below the effective power range of the measurement device. Therefore the measured value is only an approximate value.

Measurement

For measurement, an Energy Logger 4000 device was used. It is not the most accurate one (5 – 3500 W (± 1% + 1 count), 2 -5 W (± 5% + 1 count), < 2 W (±15% + 1 count)), especially in the lowest measurement range. Still, the values measured should povide an impression of the power consumption in the different operational modes of the NAS.

For off, system hibernation, HDD hibernation and idle the power consumption is an arithmetic mean over several hours.

The download and upload, values have been measured while reading/writing a 50GB file. The values bellow are mean values over the process of reading or writing, respectively. The data rates measured during this process will be published in the next post.

Surprisingly, there is no (measurable) difference in hibernation whether Wake On LAN (WOL) is on or off. That’s why there is only one system hibernation mode.

Conclusion

15.5W at max, is not so bad for a device running two hard drives. It’s idle consumption of about 12.6W still is about twice the power consumption of other devices running 24/7 (like routers).

That’s where the the system hibernation mode comes in handy. 3W in hibernation – that’s about as much as the power supply of an old desktop light consumes when the lights are off. If you use your NAS as a private storage, or even a web server that’s a very good compromise. Of course, it would be even more economical to switch the NAS completely off, when not in use. But probably not what these devices are intended for.

Thanks to the WOL functionality, you can use a hibernating NAS almost as comfortable as if it ran all day: For usage at home, the NAS can be switched on by sending a WOL package to the NAS MAC/IP address from any PC (e.g. WOL for Windows) or mobile device (e.g. Wake On Lan for android). Actually, I don’t have to do this very often as it seems that my Windows Explorer switches on the NAS as soon as it is started, for I have mounted some NAS folders as network drives.

If you want to use the NAS as a web server you can configure your router to send a WOL package to the NAS when a request is received on a certain port, for example via HTTP or HTTPs. This will switch on the device, which takes about 30 seconds, that is, the website is delivered some seconds later, once the NAS is awake. I think in private usage scenarios this should not be too much of a drawback but it safes 75% of energy.

Doing so, allows for having a NAS or even a self-hosted web server/”personal cloud” that consumes almost no energy when it is not in use. A good enough solution for my “green conscience”, at last.

By the way, a device consuming 3W consumes about 26kWh in a year, which is about 7€ (as of 2012 in Germany, the average price for electricity was 0,26€ per kWh). In comparison: A device consuming 12.6W, consumes about 110kWh a year, which is about 29€.