> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED], [EMAIL PROTECTED]
> Subject: Re: Fwd: 8 tape drives per cell?
> Allowing only 32 tapedrives is seriously shortsighted. The number of
> tapedrives directly limits the amount of data one can put in a cell;
> if you can't back it up, you should not put it in the cell.
> The ASSUMPTIONS:
> Exabyte 8200's. (That's all I have time data for.)
> Full backups must be done within a 24 hour period.
> Full backups are done one day per week.
> There are no network problems durring backups. (very optimistic)
> There are no AFS problems durring backups. (very optimistic)
> One tape takes 3 hours to write. (very optimistic)
> All tapes have no errors and are the correct length. (ify)
> backup has zero overhead per volume set. (30mins/set actually)
> use just one cell.
> The NUMBERS:
> 1 tape drive can write (24hrs/day / 3hrs/tape ) 8 tapes/day.
> in 1 day you can write (8 * 32) 256 tapes
> in 1 day you can backup 512G of data.
< omit the rest >
> // sm
> // Stergios Marinopoulos Tue Dec 8 15:37:28 1992
> // [EMAIL PROTECTED]
I think you left out one very important assumption: That you never need to restore
any of the data you spend so much time writing out. If you have to be able to respond
promptly when a customer needs data restored, you have to keep one drive idle. So
it's only 224 tapes, or 448G of data.
Mac Mathis, IBM Austin
