Adam, This is only a guess, but maybe the move nodedata command is transferring compressed data. If the data isn't being decompressed upon read and re-compressed upon write then that would explain what appears to be lower tape utilization. See what the query nodedata command shows before and after the next move. Are you seeing an increase in the number of tapes needed in the new pool compared to the old pool? It seems to me that if you were losing compression then you would see at least a doubling of the number of tapes being used in the new pool. If the number of tapes is about the same then I wouldn't worry about it. If, on the other hand tape usage is higher I'd give TSM support a call.
Rick Saylor At 07:53 AM 2/22/2006, you wrote:
We have set up a new primary storage pool, using lto2 in a 3584 library, with collocation by group. TSM5.3.2.1 on w2k3. We are moving nodedata by collocation group from the original pool to the new one in order to collocate our existing data. In the original pool we see estimated tape capacities of up to 700GB. The tapes being filled in the new pool are 280GB when 100% full. Has anyone else experienced this apparent loss of compression when moving data between pools, and what can we do to address it? Adam Crosskey The information in this e-mail, together with any attachments, is confidential. If you have received this message in error you must not print off, copy, use or disclose the contents. The information may be covered by legal and/or professional privilege. Please delete from your system and inform the sender of the error. As an e-mail can be an informal method of communication, the views expressed may be personal to the sender and should not be taken as necessarily representing the views of the Oxfordshire County Council. As e-mails are transmitted over a public network the Oxfordshire County Council cannot accept any responsibility for the accuracy or completeness of this message. It is your responsibility to carry out all necessary virus checks. www.oxfordshire.gov.uk
