FW: SUMMARY:DDS3/DLT7000

From: sriramv@wipro.co.in
Date: Sun Oct 22 2000 - 03:57:52 CDT

Maybe in reply to: sriramv@wipro.co.in: "SUMMARY:DDS3/DLT7000"
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> Hi Gurus,
>
> Following are the reply i have got. Thanks a lot to Dennis Riddick,
> Alexandre Perematko,Sydney Weinstein
>
>
> <<Re: DDS3/DLT7000>> <<Re: DDS3/DLT7000>> <<Re: DDS3/DLT7000>>
> Regs
> Sriram

attached mail follows:

# /usr/platform/sun4u/sbin/prtdiag -v

check to see how many devices are on the Board your DLT7000 is on. Your bus
could be saturated.

LMK
Dennis Riddick
SiteManager
Site Smith Inc. NYC

----- Original Message -----
From: <sriramv@wipro.co.in>
To: <sun-managers@sunmanagers.ececs.uc.edu>
Sent: Thursday, October 19, 2000 6:53 AM
Subject: DDS3/DLT7000

> Hi Gurus,
> We have a DDS3 tape and a DLT 7000 tape.
> When i take a tar or ufsdump backup on DDS3 tape its slow and on DLT7000
it
> is fast. (Its is ok)
> but when i take a cpio backup on DDS3 its fast and on DLT7000 its very
slow.
> I have 2.7 with all recommended patches. What could be the reason that
only
> cpio is slow on DLT7000.
> Thanks will summarize
> regs
> Sriram
>
> S
> U BEFORE POSTING please READ the FAQ located at
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attached mail follows:

I guess it could be an issue with block size. DDS3 ususally is slower than
DLT, but DLT may become very slow if you do not stream enough data. Try to
play with block sizes for for cpio. Another thing you may try to do is to
perform writes to the tape using dd. Feed dd with output from cpio and
ufsdump to dd and vary block size.

Alex
----- Original Message -----
From: <sriramv@wipro.co.in>
To: <sun-managers@sunmanagers.ececs.uc.edu>
Sent: Thursday, October 19, 2000 6:53 AM
Subject: DDS3/DLT7000

attached mail follows:

On Thu Oct 19 06:53:23 2000, sriramv@wipro.co.in wrote,
> We have a DDS3 tape and a DLT 7000 tape.
> When i take a tar or ufsdump backup on DDS3 tape its slow and on DLT7000
it
> is fast. (Its is ok)
> but when i take a cpio backup on DDS3 its fast and on DLT7000 its very
slow.
> I have 2.7 with all recommended patches. What could be the reason that
only
> cpio is slow on DLT7000.
> Thanks will summarize
buffer sizes and buffering.

CPIO by default uses 512byte blocks, thats real small, and causes it
to underrun the DLT7000 very often. This makes the backup slow as
the DLT7000 has to backup and restart, called shoe-shinning, as if it
was using a buff cloth on a pair of shoes.

Why is dds-3 faster on cpio, because it does not need to back up, it
can do incremental writes. So its data late error timing is less critical.

Tar uses larger blocks and ufsdump uses real big ones.

Now if you give cpio the options to write big blocks, it works better.
-C 65536 is a possibility for faster access, but its not as portable.
-C 32768 is pretty portable. And should be faster.

-- Sydney S. Weinstein, CDP, CCP Former Elm Coordinator - Current 2.5PL3 Myxa Corporation Current Elm Coordinator: elm@myxa.com syd@Myxa.COM Voice: (215) 947-9900, FAX: (215) 938-0235 Editor, Ars Ceramica, Wedgwood Society of New York: http://www.wsny.org Welcome Page: http://www.myxa.com Elm WWW: http://www.myxa.com/elm.html

S U BEFORE POSTING please READ the FAQ located at N ftp://ftp.cs.toronto.edu/pub/jdd/sun-managers/faq . and the list POLICY statement located at M ftp://ftp.cs.toronto.edu/pub/jdd/sun-managers/policy A To submit questions/summaries to this list send your email message to: N sun-managers@sunmanagers.ececs.uc.edu A To unsubscribe from this list please send an email message to: G majordomo@sunmanagers.ececs.uc.edu E and in the BODY type: R unsubscribe sun-managers S Or . unsubscribe sun-managers original@subscription.address L To view an archive of this list please visit: I http://www.latech.edu/sunman.html S T

Maybe in reply to: sriramv@wipro.co.in: "SUMMARY:DDS3/DLT7000"
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