NAS Reviews

Performance

Since the Mirra appliance can't be accessed via any method other than its own application, I could only judge file transfer speed by timing how long it took to back up folders. Mirra says that backing up a gigabyte of data takes "approximately one half-hour", but my tests show much better performance.

My test involved backing up three different folders on a 2.4GHz Pentium 4 running WinXP Home SP1 with 504MB of RAM and a 80GB NTFS formatted Maxtor DiamondMax Plus 9 ATA/133 drive. This computer was connected to the Mirra appliance via a 10/100 switch, and no other applications were active on the computer being backed up.

I ran each test twice by removing the backup with the Mirra client, then adding it back in. I started timing the transfer when the Mirra client showed that file transfer had started and stopped timing when the client showed no further transfer activity. Folder contents included a mix of file types including large JPEG images and many compressed (ZIP) files. Table 1 summarizes the results.

 

WinXP size	Mirra client size (kBytes)	# of files	Avg file size (kBytes)	Backup Time (sec.)	Backup speed (kBytes/sec)
199 MB	203,796	16	12,737	31	6574
339 MB	343,563	1828	188	334	1029
1.49 GB	1,558,805	2383	654	593	2629
Table 1: Folder Backup Test results

The results show that backup time is difficult to accurately predict, but that there is a definite trend. One could safely conclude that for equal amounts of total data, a smaller number of larger files will back up faster than a larger number of smaller files, but that's no startling revelation!

However, I'd add that the Mirra's file transfer speed compares favorably to the approximately 1-2 MBytes/sec turned in by the Tritton ASAP / ioGEAR BOSS NAS devices [revlewed here] that were tested using a similar setup, but different test method.

The other performance observation I can make is related to Mirra's transparency. Among the files that I had it watch were my Eudora email files. I thought this was a good test because I'm constantly interacting with (and checking) my mail, so the files are constantly being changed.

Mirra basically did its job without interfering with either me or Eudora, though I did notice an occasional pause, presumably because both Mirra and I wanted access to a file at the same time. At no time, however, did Mirra cause Eudora to hang or crash.

TIP: Though I had good luck with auto-backup of Eudora's mail files, Outlook users won't be so lucky. Mirra documentation notes that since Outlook locks its files, they can't be backed up while Outlook is running. As a work-around, Mirra suggests occasionally closing Outlook and leaving your computer turned on to allow Mirra to back up those files.