Asset ID:	1-71-1002802.1
Update Date:	2009-05-28
Keywords:

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Solution Type  Technical Instruction Sure

Solution  1002802.1 :   Verifying NAS Replication Source Volume Buffer Space  


PreviouslyPublishedAs
203826

Description
To check the amount of space available for a mirror buffer on the NAS Replication Master (source) server.


Steps to Follow
The NAS File Replicator mirroring feature uses a transaction journal as a mechanism to buffer file system changes as they are sent from the master (source) to the mirror (target) system. The transaction journal may also be referred to as the 'mirror buffer' or 'extended journal'.
The size of the transaction journal should be large enough, not only to buffer file system transactions as the master system sends them to the mirror system, but (often more significantly) to buffer enough transactions while the master is first replicating all the used blocks to the mirror system during initial mirror startup.

If the (initial) block replication does not complete before the buffer is filled, the only recourse is to restart the block replication.

If the master system is unable to allocate the transaction journal you may see messages in the log of the form:

Apr  2 12:23:17 nas1  kern[15892]: Creating xjournal using bulk allocation
Apr  2 12:23:17 nas1  kern[15892]: sfs2xj_create_bulk: Not enough space for xjournal bitmap (0)

To check the amount of space available for a mirror buffer:

1. Access the Sun StorageTek[TM] 5320 NAS through telnet/ssh or keyboard console.
2. When the menu prompt appears, type admin and then press the Enter key. (Since NAS OS version 4.21 you are only asked for a password before you get a prompt.)
3. Type the administrator password for the Sun StorageTek 5320 NAS, and then press the Enter key.
4. From the command line, type: fsctl frags <volume_name>

Output similar to the following is displayed:

   NAS-1> fsctl frags /vol1
/vol1: Analyzing volume. Pres ESC to abort ...
EXT FREE PAGES
0 32768
RANGE  FRAGS LOW/HIGH         PAGES SIZE(MB)
1-8     102  1/7                660 2
9-31     1   15/15               15 0
32-1024  1   623/623            623 2
> 1024  3   12479/1990856  2417415 9443
=========================================================
TOTAL   107                 2418713 9448

   The key data on this page are the third and fourth entries in the SIZE column.
Adding these two numbers returns the largest mirror buffer that can be created.

The status and size of an allocated transaction journal can be checked using the 'xj check' CLI command:

   NAS-1> xj check <VOLUME_NAME>

Example output:

   5310a > xj check /vol02test
xjournal (inode 7) size is 1325432832 bytes.
Using bulk allocation.
5310a>

Product
Sun StorageTek 5320 NAS Gateway/Cluster System
Sun StorageTek 5310 NAS Gateway/Cluster System
Sun StorageTek 5310 NAS Gateway System
Sun StorageTek 5320 NAS Appliance
Sun StorageTek 5310 NAS Appliance
Sun StorageTek 5210 NAS Appliance

Internal Comments
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The Knowledge Work Queue for this article is KNO-STO-NAS
NAS, 5210, 5310, 5320, Audited
Previously Published As
88881

Change History
Date: 2007-06-28
User Name: 71396
Action: Approved
Comment: Performed final review of article.
Updated trademarking.
Publishing.
Version: 3
Date: 2007-06-19
User Name: 71396
Action: Accept
Comment:
Version: 0
Date: 2007-06-19
User Name: 102104
Action: Approved
Comment: Made some adjustments, as new NAS OS behaves slightly different during login procedure.
Version: 0

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