Combining directories from multiple servers on a single mountpoint

Test Results

Table 2 lists the IOzone results for NFS and SSHFS from the previous article with the results for the five SSHFSM test sets:

  • Baseline: Use all system and SSHFS-MUX defaults
  • OPT1: SSHFS-MUX mount option tuning
  • OPT2: OPT1 with TCP tuning
  • OPT3: OPT2 with stronger encryption (aes-128)
  • OPT4: OPT3 with compression turned on

Table 2

Results of Five Test Sets for All Six Test

 

Sequential

     

Random

Test

Write (MBps)

Re-write (MBps)

Read (MBps)

Re-read (MBps)

Write IOPS

Read IOPS

NFS

Baseline

83.996

87.391

114.301

114.314

13,554

5,095

TCP optimizations

96.334

92.349

120.010

120.189

13,345

5,278

Baseline

SSHFS

43.182

49.459

54.757

63.667

12,574

2,859

SSHFSM

43.207

52.068

54.746

63.437

12,848

2,892

OPT1

SSHFS

81.646

85.747

112.987

131.187

21,533

3,033

SSHFSM

85.904

88.210

112.963

130.861

20,447

3,315

OPT2

SSHFS

111.864

119.196

119.153

136.081

29,802

3,237

SSHFSM

113.567

120.037

119.072

136.104

29,802

3,038

OPT3

SSHFS

51.325

56.328

58.231

67.588

14,100

2,860

SSHFSM

54.595

61.111

67.107

67.379

13,958

2,670

OPT4

SSHFS

78.600

79.589

158.020

158.925

19,326

2,892

SSHFSM

83.120

86.599

156.035

155.923

19,439

2,767

To help visualize the data, the six bar charts in Figures 6-8 plot the results for all five test sets, one for each test.

Figure 6: Plot of Baseline, OPT1, OPT2, OPT3, and OPT4 IOzone results for NFS, SSHFS, and SSHFSM for the Sequential Write (top left), Sequential Re-write (top right), Sequential Read (bottom left), and Sequential Re-read (bottom right) tests.
Figure 7: Random Write IOPS test: plot of Baseline, OPT1, OPT2, OPT3, and OPT4 IOzone results for NFS, SSHFS, and SSHFSM.
Figure 8: Random Read IOPS test: plot of Baseline, OPT1, OPT2, OPT3, and OPT4 IOzone results for NFS, SSHFS, and SSHFSM.

Comparing the performance of SSHFS and SSHFSM is rather interesting. In general, the performance is quite close except in a couple of instances. For example, in the sequential write tests, SSHFSM is sometimes up to 5 percent faster than SSHFS. SSHFSM in the OPT4 results for the sequential re-write test is almost 9 percent faster than SSHFS. For the sequential read, re-read, and random read IOPS, SSHFS is sometimes slightly faster than SSHFSM. However, this comparison might not be that useful because the "spread" of the performance results is unknown, and one can't conclusively say one is faster than the others.

Comparing SSHFS and SSHFSM performance to NFS is perhaps more useful from a qualitative standpoint. When all the SSHFMS and TCP optimizations are used, SSHFS and SSHFSM has better write performance (sequential write and re-write, and random write IOPS). Even if a stronger encryption is used, which requires more computational capability, SSHFS and SSHFSM can be just as good or better than NFS for write tests. However, read performance for SSHFS and SSHFSM is worse or only close to NFS performance until compression is turned on (compression turned on results are OPT4). A remarkable result is that SSHFS and SSHFSM performance for the random read IOPS test is never better than about 60 percent that of NFS.

Summary

SSHFS has great potential as a shared filesystem. It encrypts data in flight, it allows users to control what filesystems they mount, and it only requires an open SSH port (port 22). With some tuning, you can get SSHFS performance on the same level as NFS, except for the random read IOPS performance. However, the price you pay is data encryption or decryption on both the client and server.

In the pursuit of even more performance, I tried SSHFS-MUX. SSHFSM is derived from SSHFS and has been extended to allow several directories to be mounted in a single mountpoint. I didn't test this feature, but I did test the performance of SSHFS-MUX relative to SSHFS. Although the tests I ran here are not as extensive as those I would perform for benchmarking, casual testing allowed me to gauge general performance differences. In some cases, SSHFS-MUX was a little faster than SSHFS, but it was fairly small, only about 5 percent for some cases.

For anyone considering using SSHFS, SSHFS-MUX, with its ability to combine directories from different servers into a single mountpoint, is a definite option.

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