Drobo

FW 1.1.3 -- Abysmal write performance

After changing the privileges on the Updates folder under Applications/Drobo Dashboard to allow my limited user account to access it, the “upgrade” to FW 1.1.3 went smoothly.

However, attempts to run Xbench after that resulted in an I/O error -35. Rebooting the Drobopro twice, and then rebooting the Mac Pro finally got me past that point, so I could talk to it again.

I didn’t quite believe the first tests I ran with Xbench, as the performance was down under 30 MBPS when it had been around 70 MPBS, at least for the first iteration.

So I tried reading/uploading a 78GB test file via Finder, and I was very impressed. The performance occasionally peaked at over 104 MPBS, and most of the time it was around 75-85 MPBS. Contrary to previous results, the performance rose to a high level immediately, whereas before it started off at about 45MBPS, and after a minute or so rose to around 90. Excellent!

Then I tried writing the same file back to the DroboPro again, again using Finder on OS-X 10.6.1. Disaster!

The write speed is running around 5 to 8.6 MBPS, with a peak so far (rerunning the test) of 13.4 MPBS.

Well, maybe there is hope after all. Suddenly the speed has jumped up to around 63 MPBS, with a peak of 72 MPBS. That, I could live with, if it can be sustained. But why is the initial period so slow? Is it doing some kind of bandwidth negotiation?

Since I don’t routinely read or write such huge files (Windows XP Backup files), I will have to run more tests to see what to performance is. I’ll delay jumping off the cliff, or sending back the DroboPro, pending further results.

Stay tuned to this channel. Your mileage may vary.

Well, well, well! I stand corrected, and apologize.

This gets more and more interesting. Last night, I copied a 998 GB sparse image of a Time Machine containing about 450GB to a new volume on the DroboPro, and was pleasantly surprised to see that it was running at around 50+MBPS per the Activity Monitor, although I didn’t catch the time when it concluded.

Tonight I copied the same 72.78 GB file I have used before, from the RAID 0 hard drive on my Mac Pro to the main volume on my DroboPro, and again saw about 50+MBPS write speeds. I ran it twice, to see if there was any apparent degradation, and none was obvious. The time required was 22.5 minutes for 72.78 GB, or 53.91 MBPS average.

When monitoring the performance with Activity Monitor at the slowest update frequency (5 seconds), the rate varied between 50 and 60 most of the time, with an occasional drop into the 40s, and peaks abound 64. When monitoring using the fastest update frequency (0.5 seconds) the pattern would show some very brief drops to zero, but peaks between 85 and 90 MBPS.

All I can conclude was that when I ran the test the first time, it was right after I had hot swapped a potentially failing 1 TB WD drive and swapped in a new 2 TB drive, doing that twice, one at a time. Although the lights had all turned green before I ran the test, it is certainly possible that either the DroboPro or Mac OS was doing some kind of housekeeping or defragmentation for a period of time afterwards that would slow things down.

Now, if it was the DroboPro, and some new I/O started up, wouldn’t it make sense to quiesce the housekeeping? Once the party starts, you don’t want the maid running around with the broom!

BTW, has anyone noticed that whenever you empty the trash on Snow Leopard 10.6.1, it now empties it securely, presumably with a multi-pass erase? It didn’t used to do that – it took a special menu command. Of course I used that for anything that is remotely sensitive, but for non-sensitive stuff like music files, I would like to be able to speed it up a bit. I’m in the process of trying to delta about five copies of the test file I used, and Activity Monitor is showing the same pattern – very brief drops to zero bytes, peaks of 83MPBS, and an eye-ball average around 50 something. Even after clicking on the Stop X, it won’t stop.