TAPESIZE & LTAPESIZE

Posted in 1999

Yerli, Gursoy — Tue, 23 Mar 1999 09:07:31 -0600 — source: Informix-list mailing list archive (1991-1998)

Hi all, We have 2 (two) 12GB tape devices for data and log backups. Is it good to set TAPESIZE and LTAPESIZE as 12,288,000 or leave some cushion space ? Thank you. * MS Windows NT 4.0 SP 3 * Informix DS 7.23 TC1 Gursoy YERLI

↪ replying to Yerli, Gursoy

Art S. Kagel — Tue, 23 Mar 1999 14:42:09 -0500 — source: Informix-list mailing list archive (1991-1998)

Yerli, Gursoy wrote: > > Hi all, > > We have 2 (two) 12GB tape devices for data and log backups. Is it good > to set TAPESIZE and LTAPESIZE as 12,288,000 or leave some cushion space > ? Thank you. > > * MS Windows NT 4.0 SP 3 > * Informix DS 7.23 TC1 It depends. Is the drive native 12GB or 6GB native & 12GB compressed? If compressed capacity is 12GB leave up to 30% headroom (ie make the capacity 9GB) unless all of your data is text because the simple compression algorithms built into tape drive firmware get 50% compression from text but as little as 15% from binary data so if you have a mix you can figure between 20 and 40% compression (ie 7.5GB -> 10GB is more realistic). And remember that a capacity that works today may run out of space next year or next week as the mix of text and binary changes. (BTW treat extended character sets and GLS data (NCHAR) as 50% binary for estination purposes.) Art S. Kagel