ADSM-L

LTO3 tape capacity

2005-09-25 10:46:10
Subject: LTO3 tape capacity
From: Alexander Lazarevich <alazarev AT ITG.UIUC DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Sun, 25 Sep 2005 09:45:51 -0500
TSM 5.3.1 on win2K server.

We have a new LTO3 library, Overland Neo 4100 with 2 HP LTO3 drives. TSM
is handling the tape drivers, version is 5.3.1.something.

I've got an odd capacity issue with LTO3 volumes, and I'm not sure where
the problem lies. So, here's the info:

tsm:>q drive format=detail
                                Library Name: LB6.0.0.3
                                  Drive Name: MT1.0.0.3
                                 Device Type: LTO
                                     On-Line: Yes
                                Read Formats:
ULTRIUM3C,ULTRIUM3,ULTRIUM2C,ULTRIUM2,ULTR-
                                               IUMC,ULTRIUM
                               Write Formats:
ULTRIUM3C,ULTRIUM3,ULTRIUM2C,ULTRIUM2
                                     Element: 480
                                 Drive State: EMPTY
                                 Volume Name:
                                Allocated to:
                                         WWN: XXXXXXXXXXXXX
                               Serial Number: XXXXXXXX
              Last Update by (administrator): XXXXXXXX
                       Last Update Date/Time: 09/14/2005 11:24:34
Cleaning Frequency (Gigabytes/ASNEEDED/NONE): NONE

This is one of the LTO3 drives, notice the ultrium3 read/write, so it's an
LTO3 drive.

tsm: ITG-TSM>q vol stgpool=lto3pool
Volume Name                 Storage        Device        Estimated
                            Pool Name      Class Name     Capacity Pct
------------------------    -----------    ----------    --------- ----
ITG001L3                    LTO3POOL       LTOCLASS2     800,000.0 20.5
Filling
ITG002L3                    LTO3POOL       LTOCLASS2     386,496.7 90.2
Full
ITG003L3                    LTO3POOL       LTOCLASS2     800,000.0 19.4
Filling
ITG004L3                    LTO3POOL       LTOCLASS2     800,000.0 26.8
Filling
ITG005L3                    LTO3POOL       LTOCLASS2     800,000.0 2.3
Filling
ITG006L3                    LTO3POOL       LTOCLASS2     800,000.0 1.8
Filling
ITG007L3                    LTO3POOL       LTOCLASS2     800,000.0 1.4
Filling
ITG008L3                    LTO3POOL       LTOCLASS2     800,000.0 0.0
Filling
ITG009L3                    LTO3POOL       LTOCLASS2     386,997.2 99.9
Full
ITG010L3                    LTO3POOL       LTOCLASS2     800,000.0 0.3
Filling
ITG011L3                    LTO3POOL       LTOCLASS2     385,896.1 96.9
Full
ITG012L3                    LTO3POOL       LTOCLASS2     800,000.0 25.7
Filling

Then, notice the volumes in the LTO3POOL are LTO3 tapes, 800GB capacity,
compressed that is, and should be 400GB native.

However, also notice that the pct util is off. For example, volume
itg009l3, which is an LTO3 400GB native volume, is marked as 99.9% Full,
yet it's capacity is only 387GB. In fact, every Full volume is at a
capacity of less than the 400GB native.

Now, I do realize that expire inventory will decrease the capacity of a
volume while it's still marked as Full. However, all LTO3 tapes in my
library are getting marked 100% Full at a capacity LOWER than the native
400GB.

A 400GB native volume should be able to hold at least 400GB. Unless
compression was somehow not working, in which case 400GB would be the
maximum capacity.

Since these HP drives use hardware compression, how do I double check that
it is actually enabled? I thought the drives came
auto-compression-enabled? My older LTO2 drives just compressed
automatically.

My next step is to talk to Overland, but I thought I'd ask here first.

Any ideas?

Thanks in advance,

Alex

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