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 🙂

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