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What each of SIZE_DATA_BUFFERS_xxx exactly do?

AlChie
Level 4

Greetings!

I would like to understand how does all SIZE_DATA_BUFFERS_xxx get implemented.

Let me first explain how my enviroment looks like:

I have a media server (server for NDMP) , 5 filers connected to it via LAN and a library (which is VTL) with 50 drives. Every 10 drives from those are zoned to each filer directly and also 10 drives zoned to media server except ONE filer which uses drives on media server and flows backup traffic via LAN and from media server to library.

So as you may see it is an NDMP backup.

The filer that uses media server's drives is EMC Cellera and had bufsize set to default value of 128K.

So I decided to make an equal BUFFER SIZE on both media server and filer by creating SIZE_DATA_BUFFERS_NDMP with needed value in it. I was very surprised to see that backup of this filer didn't use that option and insted used SIZE_DATA_BUFFERS which i have increased to 512K for disk backups of DataDomain (just FYI).

But other NAS filers backups which had been directly zoned to library drives did used that entry and set this value to value in touch file.

May you be so kind to unveil the truth for me....

 

 

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Best Regards, AlChie
1 ACCEPTED SOLUTION

Accepted Solutions

Marianne
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Have you perhaps had a look at the NetBackup™ Backup Planning and Performance Tuning Guide ? 

See this topic on p.122 : 

Note on shared memory and NetBackup for NDMP

Table 7-7 :
Local NDMP backup or three-way backup: 
NetBackup does not use shared memory (no data buffers). You can use SIZE_DATA_BUFFERS_NDMP to change the size of the records (not buffers) that are written to tape. Use SIZE_DATA_BUFFERS_DISK to change record size for NDMP disk backup.

Remote NDMP backup:
NetBackup uses shared memory. You can use SIZE_DATA_BUFFERS_NDMP to change the size of the memory buffers and the size of the records that are written to tape. Use SIZE_DATA_BUFFERS_DISK to change buffer size and record size for NDMP disk backup.

I found TNs related to NDMP buffer size and bugs in 6.5.x and 7.x, but nothing for 8.0. 
So, the assumption is that the buffer config should work as per the above documentation. 

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RiaanBadenhorst
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Those files only apply when you're writing directly to storage, i.e. the media server to DD (using 512k) or the Filer to VTL (using 128k). 

When the filer writes across the network the media server becomes the receiver and the writer of the data, so the filer's 128k doesn't apply and the media server writes the stream to DD using 512k blocks.

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

Have you perhaps had a look at the NetBackup™ Backup Planning and Performance Tuning Guide ? 

See this topic on p.122 : 

Note on shared memory and NetBackup for NDMP

Table 7-7 :
Local NDMP backup or three-way backup: 
NetBackup does not use shared memory (no data buffers). You can use SIZE_DATA_BUFFERS_NDMP to change the size of the records (not buffers) that are written to tape. Use SIZE_DATA_BUFFERS_DISK to change record size for NDMP disk backup.

Remote NDMP backup:
NetBackup uses shared memory. You can use SIZE_DATA_BUFFERS_NDMP to change the size of the memory buffers and the size of the records that are written to tape. Use SIZE_DATA_BUFFERS_DISK to change buffer size and record size for NDMP disk backup.

I found TNs related to NDMP buffer size and bugs in 6.5.x and 7.x, but nothing for 8.0. 
So, the assumption is that the buffer config should work as per the above documentation.