Re: Backup options

No William

However, Im saying that comparing FC attached disk and SCSI attached disk 
is like comparing a pear to an apple.

The inital statement was that drives where quicker than disk.

I then went on saying that this is not always true, as the fact that disk 
is fast than tape is not always true as well.

It all comes down to:

1. The type of data your backing up/restoring
2. The type of infrastructure you're using.
3. The amount of devices you have attached on a single devicechain.

For example; a LTO-2 drives outruns internal SCSI disk in most cases. It 
even does this with smaller files due to the fact LTO-2 has dynamic speed 
ratio. This makes it possible to have a lower streamrate compared to LTO-1 
thus making it possible to send small files(utilizing large transaction 
sizes) to tape with a fair speed.

FC attached disk, correctly configured, outruns most tape drives. It does 
this mainly with small-to-medium files but can outrun tape drives even 
with bigger files up to a certain limit.

What I'm trying to say is that there is no rule. It all depends on how you 
have configured the system, what kind of data that is transmitted and how 
it is configured to be transmitted.

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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2004-11-09 14:14
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Re: Backup options






I am trying to understand where you are coming from.  See if I have this
correct.

Are you saying FC attached Tape drive vs SCSI attached Disk?

I have SCSI attached Tape drive and SCSI attached Disk.



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


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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>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
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
                      <Daniel.Sparrman@        To: ADSM-L AT VM.MARIST DOT EDU

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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