So the minimum speed of a TS1120 is 35 MB/s, not 40. My statement
remains the same. Take 35 MB/s, multiply it times your compression
ratio, and you've got the minimum speed of a TS1120. Most people get
about 1.5:1, so that makes it a 52.5 MB/s minimum speed drive.
You also said:
>It's true that if I have a fileserver backup the don't full fill the
data
>buffer of the tapes (LTO - SDLT - Magstar), maybe for LAN backup or for
the
>tipically fileserver file type (hundreds - small file) the problem will
be
>for each tape technologies... BUT the Virtual Backhitch of the TS1120
will
>help you and for some tests that we made it's really true... If you
backup
>Big database 10 TB(ORACLE with RMAN and 8 allocate channel) we reach
140
>GB/h one drives... (with 4 drives parallell 140*4!!!)...
I hate to say it, but you're not filling the buffer. AT 140 GB/hr,
you're getting 39 MB/s, which isn't 52.5, the minimum speed if you're
getting 1.5:1.
So let's get to the "virtual back hitch." It cracks me up. It allows
them to write to "alternate sections of tape" to prevent real
backhitches. What the heck does that mean?
Think through this. The tape's going along at 100 miles an hour (i.e.
100 inches per second or so) and the buffer runs out of stuff. The
tape's not supposed to backhitch, so what does it do? It just keeps
going! It keeps streaming along and just stops writing data until it
gets some more data! So instead of shoe-shining, you get wasted tape.
Wow.
---
W. Curtis Preston
Author of O'Reilly's Backup & Recovery and Using SANs and NAS
VP Data Protection
GlassHouse Technologies
-----Original Message-----
From: marco chiapusso [mailto:mchiapusso at hotmail.com]
Sent: Thursday, December 14, 2006 4:00 AM
To: Curtis Preston
Cc: veritas-bu at mailman.eng.auburn.edu
Subject: Re: [Veritas-bu] Shoe shining
Curtis,
what you said it's partially true...
The new generation TS1120 gen 2 have that specification
Native data rates 104 MBps
Adaptive data rates 104, 85, 70, 55, 41 and 35 MBps
What you described it's not exactly shoeshining.
It's true that if I have a fileserver backup the don't full fill the
data
buffer of the tapes (LTO - SDLT - Magstar) ,maybe for LAN backup or for
the
tipically fileserver file type (hundreds - small file) the problem will
be
for each tape technologies... BUT the Virtual Backhitch of the TS1120
will
help you and for some tests that we made it's really true... If you
backup
Big database 10 TB(ORACLE with RMAN and 8 allocate channel) we reach 140
GB/h one drives... (with 4 drives parallell 140*4!!!)...
Regards!!
>From: "Curtis Preston" <cpreston at glasshouse.com>
>To: "Peter Marelas" <peter_marelas at symantec.com>
>CC: veritas-bu at mailman.eng.auburn.edu
>Subject: Re: [Veritas-bu] Shoe shining
>Date: Thu, 14 Dec 2006 04:36:00 -0500
>
>I've been a fan of this for a while. Too bad only one vendor supports
it
>in their tape library (Qualstar).
>
>---
>W. Curtis Preston
>Author of O'Reilly's Backup & Recovery and Using SANs and NAS
>VP Data Protection
>GlassHouse Technologies
>
>
>-----Original Message-----
>From: Peter Marelas [mailto:peter_marelas at symantec.com]
>Sent: Thursday, December 14, 2006 12:37 AM
>To: Curtis Preston; marco chiapusso; Greg.Hindle at constellation.com
>Cc: veritas-bu at mailman.eng.auburn.edu
>Subject: RE: [Veritas-bu] Shoe shining
>
>This will solve your shoe-shining problem.
>
>HDD in a tape cartridge and tape drive emulator.
>
>http://www.imation.com/products/ulysses/index.html
>
>Regards
>Peter Marelas
>
>-----Original Message-----
>From: veritas-bu-bounces at mailman.eng.auburn.edu
>[mailto:veritas-bu-bounces at mailman.eng.auburn.edu] On Behalf Of Curtis
>Preston
>Sent: Thursday, 14 December 2006 5:32 PM
>To: marco chiapusso; Greg.Hindle at constellation.com
>Cc: veritas-bu at mailman.eng.auburn.edu
>Subject: Re: [Veritas-bu] Shoe shining
>
>I hate to say it, but your IBM sales rep is either lieing or doesn't
know
>what he/she's talking about if he/she told you that their drives don't
>suffer shoeshining. (Don't worry; he/she is not alone.)
>
>The TS1120 is still a streaming tape drive and streaming tape drives
have a
>minimum speed. The TS1120's minimum speed is 40 MB/s times your
>compression ratio (avg 1.5:1), which makes it about a 60 MB/s minimum
speed
>tape drive. If you're not sending significantly less than 60 MB/s to
that
>drive, it is shoe-shining. The same is true for the T10000 from STK
and
>LTO-3. LTO-3's minimum speed is 27 MB/s, T10000's is 50 IIRC. Not
sure of
>the minimum speed for SDLT.
>
>Here's an article I wrote about this problem:
>http://tinyurl.com/ym2sap
>
>
>
>---
>W. Curtis Preston
>Author of O'Reilly's Backup & Recovery and Using SANs and NAS VP Data
>Protection GlassHouse Technologies
>
>-----Original Message-----
>From: netbackup-bounces at backupcentral.com
>[mailto:netbackup-bounces at backupcentral.com] On Behalf Of marco
chiapusso
>Sent: Wednesday, December 13, 2006 7:53 AM
>To: Greg.Hindle at constellation.com
>Cc: veritas-bu at mailman.eng.auburn.edu
>Subject: Re: [Veritas-bu] Shoe shining
>
>Yes sure,
>the only one that I know that are not affected of that problem are the
IBM
>Magastar tape (TS1120)
>
>Bye
>
> >From: "Hindle, Greg" <Greg.Hindle at constellation.com>
> >To: "NB List Mail" <veritas-bu at mailman.eng.auburn.edu>
> >Subject: [Veritas-bu] Shoe shining
> >Date: Wed, 13 Dec 2006 09:41:46 -0500
> >
> >How can I tell if my SDLT and LTO3 drives are show shining?
> >
> >
> >Greg
> > >>> This e-mail and any attachments are confidential, may contain
> > >>> legal,
> >professional or other privileged information, and are intended solely
> >for the addressee. If you are not the intended recipient, do not use
> >the information in this e-mail in any way, delete this e-mail and
> >notify the sender.
> >CEG-IP2
>
>
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