Edit: The links at the end no longer work.
Originally posted November 10, 2009 on AIXchange
For a while now customers have been asking me how to identify the filesystems and physical and logical volumes that are good candidates to move to solid state drives (SSDs). Given these drives’ I/O characteristics and the higher prices they currently command, you should be selective about the data you move from traditional drives to SSDs.
Obviously you don’t want to put seldom-used data on these pricey new drives–just leave that on your older, slower disks. Your SSDs should house critical, heavily used data. Fortunately, figuring out how to get the most from your SSDs just got easier.
The latest AIX releases–5.3 TL11 and 6.1 TL4–include new options that can help you determine the data that’s best suited for SSDs. I updated some of my machines so I could test out these new options, and they seem to work as advertised.
The key new option is found with the filemon tool and its new flag, -O hot, which creates a report that shows you your most frequently accessed data.
To receive my filemon output, I ran:
filemon -O hot -A -x “sleep 20” -r fmon -o fmon.out
Incidentally, -O hot must run in conjunction with the -A flag to enable automated offline mode. It cannot run in realtime mode. I know this because I tried and received this error:
filemon -O hot -o fmon.out
hot option not supported in realtime mode.
Once I had my output file, I ran trcrpt:
trcrpt -r fmon.out > fmon.rpt
Then I viewed a report showing me hot files, hot logical volumes, and hot physical volumes by running: more fmon.rpt
I intentionally ran the trace ran at a time where my disks were heavily utilized. Actually, it may make sense for you to run these traces several times, especially during peak workloads. This will give you a good idea about which files and physical and logical volumes may be good candidates for moving to SSDs.
This data will greatly help you make informed decisions about moving filesystems and physical and logical volumes to SSD.
While I do regularly work with and speak to customers, SSD is fairly new technology, so there’s plenty more to be learned about how people are using these new drives. So please enlighten me and your fellow readers by sharing your experiences with SSDs in Comments.
On an unrelated note, I saw these interesting articles about tech support for the International Space Station that I thought I’d pass on.