ADSM-L

Re: [ADSM-L] Who/What determines tape compression

2007-04-30 16:15:35
Subject: Re: [ADSM-L] Who/What determines tape compression
From: Zoltan Forray/AC/VCU <zforray AT VCU DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Mon, 30 Apr 2007 14:45:58 -0400
You may be right about the encryption "feature".  For this devclass, it
was set to DRIVEEncryption=Allow, which says "the hardware or library
determines...." and I'll bet the drive default is to encrypt.  I was able
to manually update the devclass to set it off.

I was wondering if my Atape level has something to do with it since I am
below the level the readme says is GA for encryption. I really don't want
to much with these downlevel systems that I am working toward removing,
although I might have to.

When we ordered these drives, IBM said "they come with encryption - you
can not remove it".

Anyone know at what TSM server level the DRIVEEncryption option was
introduced ?

----------------------------------------------------
Zoltan Forray
Virginia Commonwealth University
Office of Technology Services
University Computing Center
e-mail: zforray AT vcu DOT edu
voice: 804-828-4807



Curtis Preston <cpreston AT GLASSHOUSE DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
04/30/2007 02:00 PM
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Subject
Re: [ADSM-L] Who/What determines tape compression






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:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Zoltan Forray/AC/VCU
Sent: Monday, April 30, 2007 10:13 AM
To: ADSM-L AT VM.MARIST DOT EDU
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: zforray AT vcu DOT edu
voice: 804-828-4807

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