The recovery time is dependent on the type of data. Restoring +2 million 
files directly from tape is probably  not an option. However, restoring 
files >500MB from tape is faster.

Restoring large files from disk is slower than restoring the same file 
from tape. Dont know why but I guess it has todo with the random I/O 
structure of disk compared to the sequential I/O strategy of tape. With 
disk, you dont have the same type of streaming capability as you have with 
tape.

As I said earlier, the case here is not internal SCSI/SCSI attached disk. 
We're talking FC attached disks utilizing multiple FC HBA:s. Tape will 
almost at every occation outrun native SCSI attached disk drives.

Best Regards

Daniel Sparrman
-----------------------------------
Daniel Sparrman
Chef Utveckling & Drift
Exist i Stockholm AB
Propellervägen 6B
183 62 TÄBY
Växel: 08 - 754 98 00
Mobil: 070 - 399 27 51



William Rosette <Bill_Rosette AT PAPAJOHNS DOT COM> 
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2004-11-08 17:34
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Re: Backup options






Question on the disk vs tape speed.  When you say the tape equals disk,
does this also include recovery time.  I've noticed disk is incomparable 
in
recovery versus tape especially when you go to more then 1 tape, maybe
because I live in the bottom SCSI world.  Thanx

Thank You,
Bill Rosette
Data Center/IS/Papa Johns International
WWJD


  
                      Daniel Sparrman   
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Allen,

we have disk performing up to 280MB/s over 2 FC HBA against a FAStT900.
You know the amount of tape drives you would need to match that speed? I'd
say about 4-5 LTO-2 tape drives.....

No problems matching disk speed against tape speed. Only a matter of
budget :)

But I do agree with you in your basic opinion. If you've got a limited
budget, a single LTO-2 drive is normally faster than running against
internal SCSI-disks or S-ATA disks.

Best Regards

Daniel Sparrman
-----------------------------------
Daniel Sparrman
CIO
Exist i Stockholm AB
Propellervägen 6B
183 62 TÄBY
Växel: 08 - 754 98 00
Mobil: 070 - 399 27 51



asr AT UFL DOT EDU
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2004-11-08 17:19
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==> In article <OF4F01CECE.433776B6-ON85256F46.005486D5 AT papajohns DOT com>,
William Rosette <Bill_Rosette AT PAPAJOHNS DOT COM> writes:



> It is currently running at 55.945 GB per hour going to tape (1 tape
drive
> (collocate)), pretty good for tape drive speed.  Disk would make the
backup
> run faster with multi-streams.  Cannot go to multi-tapes due to slow
> recovery.  Other option would be to break the backup into 2 separate
backups
> running simultaneously, probably nightmare admistrativewise.

Say more about "slow recovery" when you do mulitple sessions to tapes?

If you've got the disk to sustain the backup, that will help, but I've not
yet
seen a disk solution that measures up to the tape speeds.


 - Allen S. Rout