If the encryption feature is enabled and not working correctly, your compression would disappear. It's supposed to compress before it encrypts, and you should be able to turn encryption on and off, and I would guess the default would be off. Either way, it shouldn't change your compression. But what if it is enabled and isn't compressing before encrypting? That would remove any compression.
Another idea is that whatever flag is set on the OS side to tell the drive to compress isn't getting set. Or it's being told to compress, and it's ignoring that flag. My first response would be to call IBM support and ask why your new drives aren't compressing data. Just curious. Who told you that you had to buy the encryption option? Is it that the drives don't come without it any more? --- W. Curtis Preston Author of O'Reilly's Backup & Recovery and Using SANs and NAS VP Data Protection GlassHouse Technologies -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Zoltan Forray/AC/VCU Sent: Monday, April 30, 2007 10:13 AM To: [email protected] Subject: [ADSM-L] Who/What determines tape compression TSM servers - AIX v5.3.4.1 AIX 5.1 (yes I know...unsupported....working to phase out and replace with Linux servers). I am currently dealing with a strange issue relating to data compression levels (or the lack there-of) I am hoping someone can explain or point-out where to look. We originally had 4-3592E05 drives in our 3494 tape library. We just added 3-more. FWIW, these drives have the new "encryption" feature (we didn't ask for it.....were told we had to take it.....cost us $3,000 more). Ever since we added the new drives, I am noticing a drop in the compression I am achieving from these drives on the AIX TSM server that owns the library. Before these new drives were installed, I achieved 1.8TB on one cartridge owned by this server. I didn't do much 3592 usage since I simply didn't have the drives to share amongst 4-servers. Since these new drives have been put into use and I have agressively started migrating data from 3590K tapes, I am only seeing <600GB per cartridge. This is almost no compression at all. I did a complete removal and re-add of all AIX tape and TSM devices and bounced the TSM server. It is obviously seeing and using them, with no issues. All drives have the latest firmware, D3I1_A38. Nothing has changed with the DEVCLASS. All 3592's are using the same devclass. It is configured as 3592-2C. Scaled at 100%. No, I can't say that the lower compression is coming from the new drives, only. Any thoughts on what gives ? Why the change in compression ratio (this is a high-mix of various kinds of data. I should be getting at least 1TB vs my Notes systems which can't compress much and I get around 700-800GB per cartridge). ---------------------------------------------------- Zoltan Forray Virginia Commonwealth University Office of Technology Services University Computing Center e-mail: [EMAIL PROTECTED] voice: 804-828-4807
