Veritas-bu

Re: [Veritas-bu] block size for restore

2009-02-19 12:42:31
Subject: Re: [Veritas-bu] block size for restore
From: Jon Bousselot <jon-bousselot AT pacbell DOT net>
To: Justin Piszcz <jpiszcz AT lucidpixels DOT com>
Date: Thu, 19 Feb 2009 09:26:32 -0800
Both libraries and drives are on the same media server, which is also 
the master server.  It's a small but critical deployment.  Setting the 
buffers makes both drives run at 32k blocks, so we're not even close to 
getting maximum throughput here. That would be okay while I get the 
LTO-1 copied to the LTO-4 media.

In the bptm logs, it says the LTO-1 tape is written in 64k blocks, but 
something is complaining about only supporting 32k blocks.  The weird 
part is this system wrote those tapes, using the very same LTO-1 
hardware.  I have been poking around the registry to see if I can find a 
hard coded entry for the tape driver that defines a 32k block size 
limit.  I've found nothing so far.

I think we might be able to find enough hardware to build a linux system 
to host the LTO-1 drives and bypass any driver compatibility issue with 
tape blocks.  In this way we can isolate media we are certain from 
drivers we are uncertain.  And then I can set the LTO4 block size to 
whatever maximum I can get windows2003 to handle. 

I think it is a driver problem.




> So you have the BUFFER size as 32k for LTO-1 and 64k or greater for 
> LTO-4? sounds like you need one media server to have the buffer_size 
> set for the LTO-1 drives and the other media server set to the other?
>
> Some of the parameters:
> NUMBER_DATA_BUFFERS
> NUMBER_DATA_BUFFERS_RESTORE
> SIZE_DATA_BUFFERS
> SIZE_DATA_BUFFERS_DISK
>
> First thing first, is the LTO-1 drive on its own media server where no 
> other drives are attached (e.g., LTO-4?)
>
>
> On Wed, 18 Feb 2009, Jon Bousselot wrote:
>
>> Ooops, I didn't put enough details here.
>> The LTO-1 drive/library is still attached to its original scsi
>> controller on the host.  I added a new scsi card for the LTO-4 library.
>>
>> The task I need to accomplish is to duplicate selected images from the
>> LTO1 media onto the LTO4 media, and then the LTO1 hardware goes away.
>>
>>
>>
>>> My understanding is that LTO4 drives are not backwards-read 
>>> compatible with LTO1.  Only LTO2 & LTO3.
>>>
>>> LTO = Read 2 versions Back, Write 1 version Back.
>>>
>>> -Jonathan
>>>
>>> ________________________________
>>>
>>> From: veritas-bu-bounces AT mailman.eng.auburn DOT edu on behalf of Jon 
>>> Bousselot
>>> Sent: Wed 2/18/2009 2:26 PM
>>> To: veritas-bu AT mailman.eng.auburn DOT edu
>>> Subject: [Veritas-bu] block size for restore
>>>
>>>
>>>
>>> This one has me stumped.
>>> Windows 2003 with all the latest patches.
>>> Media written since 2003 shows up in the bpimagelist -L as having a
>>> media block size of 65536.
>>>
>>> Upgrade to 6.5.3
>>> SIZE_DATA_BUFFERS must now be 32768 because if it is anything else, I
>>> get media write errors.
>>>
>>> When I try and restore data, the bptm logs show this
>>>
>>>
>>> 2/17/2009 1:46:05 PM - Error bptm(pid=1996) tapemark or blank tape
>>> encountered reading media header, drive index 1
>>> 2/17/2009 1:46:06 PM - Error bptm(pid=1996) The tape device at index 1
>>> has a maximum block size of 32768 bytes, a buffer size of 65536 cannot
>>> be used
>>> 2/17/2009 1:46:06 PM - Error bptm(pid=512) The following files/folders
>>> were not restored:
>>>
>>>
>>> I cannot read the old LTO-1 tapes.  They were stored at Iron Mountain
>>> safely, and I tried more than three tapes from various years.
>>> I verified the hotfix numbers for tape.sys and even tried updated tape
>>> drive drivers with no success.
>>>
>>> NB docs (perf tuning guide) say the SIZE_DATA_BUFFERS is not even used
>>> during a restore operation.
>>> Is there a registry key that is forcing the drive to only accept 32k
>>> blocks?
>>> The LTO-4 drive is working just fine even at the 32k block size.
>>>
>>> -Jon Bousselot
>>> _______________________________________________
>>> Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
>>> http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
>>>
>>>
>>>
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>>
>
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