Managing RAW Volumes

Well I was recently called by another IBMer and asked how to use RAW volumes. The person called to ask why sometimes DSMFMT will format quite fast on one machine then take forever on another machine. Well one thing you have to understand about DSMFMT is that it's taking that file and making the space within it RAW. If you've ever looked inside an unused TSM volume you'll see it is a text file filled with ADSM over and over (they might have changed the fill but when I was teaching TSM thats what we saw). So why use RAW instead of actual files (other than files being a redundant process)? FAST! EASY! and when speed in DR is key it's the only way to go. It's actually easier than one would think and with a little script you can manage your RAW volumes and hdisks easily. I'll post the script along with a script to querry the serial and WWN of your tape drives. These two scripts come courtesy of Hari Patel my co-worker who is a PERL mad man. (Download tar/zip)

The Case For Raw Volumes!

If you are serious about TSM server rebuild times and want the quickest way to get up and running then I suggest you look into raw logical volumes for all your TSM DB, Log, and storage needs. Of course if you are running on NT I can't say I know of any way TSM can use raw, but in our AIX shop we live by raw volumes. The creation time is quick and with a little script I can have my volumes created and ready for the DB restore in no time. I have been down the road of DSMFMT and know how long large volumes can take to create and since TSM does not like more than 16 volumes some older Unix servers can take time to format. The other nice thing about raw volumes is if the server crashes its rare, except for disk failure, for volume corruption to occur. I have had too many dirty super blocks to deal with in my time, and I don't miss them. Remember, all TSM is really doing with DSMFMT is creating a file and in a way converting it back into raw. So why do the extra steps, save yourself some time if you ever are in a true DR situation.