[Updated Sept 25, 2008: Firmware 1.2.4 was released and has improved performance over what’s mentioned here. I write about Firmware 1.2.4 here.]
Back in July I mentioned I was getting a Drobo to try and clean up my hard drive mess. I’ve had the Drobo for about a month now but haven’t posted about it because I’m still fighting with it. Overall it works fine but performance has been poor. After tweaking, there’s still a lot of variation in performance which bugs me. Drobo has said that write speeds of 34MB/sec and read speeds of 52MB/sec through FW800. I’m seeing less than half that.
My Drobo contains four 1TB Western Digital Caviar Green Drives and is connected to my Mac with FW800. Typically it’s chained with a Western Digital MyBook drive although for my testing I’ve removed the MyBook to eliminate it or the chain as a possible cause. I haven’t noticed any difference by doing this.
At one time spotlight was indexing the drive. At that time I was seeing extremely poor performance (4MB/sec) much of the time. My iTunes music files are on the Drobo and there were times where audio playback would freeze, previously unheard of on my iMac. At these times Activity Monitor would show that all disk activity had stopped. Since nothing else was going on it hit me that it might be spotlight so I excluded the drive. This helped but performance didn’t skyrocket, I would see 10MB/sec.
I had Time Machine using the drive in the beginning and there were times I noticed a slowdown and looked up and saw Time Machine was active. My Time Machine backups tend to be small as I exclude anything large and concentrate on documents, scripts and images. Once I started paying attention I noticed that things seem to be fines for many Time Machine backups but if the backup was over 150MB (roughly) the backup would slow down around the 130MB mark and overall Drobo performance also slowed. Hard to say exactly what Time Machine was doing. I set Time Machine to only run manually which helped add consistency to the Drobo performance.
I noticed that iTunes playback would stutter at what seemed like random times. This ended up not being random but happened when iTunes had downloaded something in the background (such as a podcast) and was adding it to the library. I moved the iTunes database file back to my system drive but kept the music folder on the Drobo and this resolved the stutter problem.
At this point I had done all the tuning I felt I could do and decided to start testing some file copies.
Copying a set of files (about 8GB with seven 1GB files and about 20 other files) results an average speed of about 15MB/sec with peaks at 25MB/sec. This is while nothing else is going on with the Mac.
If I start copying larger files (approx 1GB each) and I’m seeing throughput of 15MB/Sec but I then start a second copy containing many small files the overall performance of the drive (as shown in Activity Monitor) drops to a peak of 4MB/sec. Along these lines, if I start a ChronoSync job the analyze phase drops the throughput of any existing copy to a crawl. Things pick up once the anaylze is done and the file copy begins. It appears that any activity requiring rapid disk queries slows down the Drobo. It’s not just the file copy that slows, but total disk throughput drops to less than 200KB for reads (that’s not a typo, it’s KB).
When I was seeing poor performance I decided to pop out a drive and let it rebuild, to see if that helped.It didn’t. Interestingly, I did didn’t see a degradation in performance during the rebuild process.
Early on I did try running a Parallels virtual machine off the drive and performance was OK but not great. But in this case I didn’t blame the Drobo as it didn’t feel much slower than back in the days when I ran it off the system drive. I’ve been running my VMs off a dedicated external firewire drive for awhile now and didn’t expect this to change.
At this point in time I’m planning rebuilding the Drobo. Partly to see if it helps and partly to reconfigure it before I get too far in. While I’m not very happy with the performance I’ve decided to keep it and either see if things improve or rethink how I’ll use it. Combined with the poor small file performance it appears the Drobo has a harder time processing many files in a small time frame. It may not be suitable for me to use for live files.
Once I rebuild the Drobo I’ll do some more performance testing. If things don’t improve I’ll use it as a backup drive only. I had planned to use it to store my active photo libraries, active iTunes library and some other files. Instead the active copies of these might reside on my Windows Home Server and I’ll back them up to the Drobo. At this point I get better performance accessing my Windows Home Server over the wired network than I do from the Local Drobo. When I rebuild the Drobo I’m going to withhold a couple of drives so I can add them to my Home Server if I go that route.
I haven’t contacted Drobo support yet since I’m not really at a point where I can say the Drobo is defective, but their support structure is worth mentioning.
The Drobo comes with a 1 year warranty (short in my opinion) with additional years of “Drobocare” costing $49/year. Drobocare is like an extended warranty that includes software upgrades. Critical software fixes are always available, but feature updates require Drobocare.
They do have a online support forum but it’s restricted to current owners. To access the forums you must register and provide a serial number. But these aren’t official support forums where Drobo support techs will respond to questions (although some may do so). It’s community based support so the serial number requirement doesn’t make sense to me. It prevents potential buyers from browsing the forums. Since forums generally talk about problems but most press is positive this may be the reason.
I had hoped to use the Drobo as my primary drive for pictures and music while using it as a backup for other files. As it turns out I may go with it as strictly a backup drive.
I plan to rebuild the drive and tell it to create a 16TB volume. This will allow me to continually expand as larger drives become available and not have to worry about partitioning the drive. It’s currently set to 4GB. The only downside to the larger partition seems to be the boot up time although I’m not seeing anywhere near the 4 minute bootup time that was estimated for my 4TB partition (it’s faster).
Then I’ll create a small 300GB partition for time machine. Like I said, I back up very little through time machine and in two months it filled about 100GB so 300GB should be fine. I’m giving Time Machine it’s own partition so it doesn’t just keep expanding forever. Everything else will be one partition.
My main disappointment is how erratic performance has been. While it’s been mentioned that the Drobo can be used as a boot drive I’m not sure I’d like the performance.
Hopefully with the Monday holiday I can have the Drobo rebuilt by this time tomorrow. Although if the speed doesn’t improve it’ll take awhile to copy those files back.