Asset ID:	1-71-1009183.1
Update Date:	2009-09-24
Keywords:

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Solution Type  Technical Instruction Sure

Solution  1009183.1 :   Sun StorEdge[TM] 9900 Series: What is the purpose of "noread" mode for ShadowImage paircreate.  


PreviouslyPublishedAs
212714

Description

The purpose of the ShadowImage paircreate -m <mode> argument "noread", may not be commonly known or understood. This is due to the lack of documentatary details, or explanation in the HDS ShadowImage (SI) and Command Control Interface (CCI) user manual.

This document provides an explanation of "noread" mode.

Steps to Follow

It is possible with the CCI paircreate command, to specify a -m <mode> for Shadowimage and TrueCopy. One argument to the -m <mode> option is "noread".

The CCI manual details that the noread argument is only applicable to Shadowimage.
The purpose of the noread argument is to hide the secondary volume (S-VOL). The S-VOL becomes read-disabled when the noread argument to the mode option is specified. The S-VOL is read-enabled when the noread argument to the mode option is omitted.

Example of CCI command for paircreate:

without mode option:

 # paircreate -g tgrp0 -vl

with mode option:

 # paircreate -g tgrp0 -m noread -vl

where,

 -g:    (group name)
-vl:   (data flow direction - local) 

It is not made clear in the CCI documentation, in which state of the ShadowImage pair the noread mode is effective. Based upon testing, and confirmation via HDS, the following information has now been obtained, that helps to clarify the intended use of the noread argument, and in which pair state the "noread" functionality applies.

The ShadowImage -m noread option only applies to the S-VOL, when the ShadowImage pair are in a *PAIR* or *COPY* status.

S-VOL STATUS     with -m noread     without -m noread
------------     --------------     -----------------
PAIR               no access           read only
COPY               no access           read only
SSUS               read/write          read/write

The purpose of the -m noread argument is to prevent users from backing up (reading) the S-VOL, while it is still linked (paired) to the primary volume (P-VOL), and therefore still changing.

Product
Sun StorageTek 9900V Series Array
Sun StorageTek 9910
Sun StorageTek 9960 System
Sun StorageTek 9990 System

shadowimage, paircreate, noread, mode, option
Previously Published As
79324

Change History
Date: 2004-12-17
User Name: 25440
Action: Approved
Comment: Added "Sun StorEdge[TM] 9900 Series" to title ('series' as this is generic per the Product list). Minor format edits. Publishing.
Version: 5
Date: 2004-12-17
User Name: 25440
Action: Accept
Comment:
Version: 0
Date: 2004-12-16
User Name: 128938
Action: Approved
Comment: I could not find any acronym use that is not explain. Hence, sending back for final review.
Version: 0
Date: 2004-12-02
User Name: 25440
Action: Rejected
Comment: Please explain the acronyms used in this document. The Sun Microsystems Editorial Style Guide states that scronyms should be expanded on first use. Thank you.
Version: 0
Date: 2004-12-02
User Name: 25440
Action: Accept
Comment:
Version: 0
Date: 2004-12-02
User Name: 26313
Action: Approved
Comment: Ready for Final Review.
Version: 0
Date: 2004-11-25
User Name: 26313
Action: Accept
Comment:
Version: 0
Date: 2004-11-25
User Name: 128938
Action: Approved
Comment: Amended document as suggested by first reviewer. Sending it again for tech review.
Version: 0
Date: 2004-11-25
User Name: 128938
Action: Add Comment
Comment: Thanks to Ross work and suggestion which make my original document more presentable and informative. I had amended it as suggested and resent for tech review.
Version: 0
Date: 2004-11-24
User Name: 26313
Action: Rejected
Comment: I have detailed some suggested ammendments in the Voyager Comments section. Please review and ammend if an agreement,
with the suggestions, and re-submit for review.

Thank you.
Version: 0
Date: 2004-11-24
User Name: 26313
Action: Add Comment
Comment: Hello Weng-Fatt.

Can I suggest a much simplified version of your document ?

I would keep the Description section similar to it is, but would take all the first person "I"
references out - This is because KA's should not be written in the - I - "first person" context.

For the Description section, I would suggest something like :

-- Start --

Due to the lack of documentatary details, or explanation in the HDS ShadowImage (SI)
and Command Control Interface (CCI) user manual. The purpose of the ShadowImage
paircreate -m argument "noread", may not be commonly known or understood.

---Then for the Document body, I would suggest similar to the following ...

It is possible with the CCI paircreate command, to specify a -m for Shadowimage and Truecopy. One argument to the -m option is "noread".

The CCI manual details that the noread argument is only applicable to Shadowimage .
The purpose of the noread argument is to hide the secondary volume (S-VOL).
The S-VOL becomes read-disabled when the noread argument to the mode option is
specified. The S-VOL is read-enabled when the noread argument to the mode option
is omitted.

--- Perhaps include some examples of the use of the paircreate command here,
with and without the -m noread option/argument ?

It is not made clear in the CCI documentation, in which state of the Shadowimage
pair, the noread mode is effective. Based upon testing, and confirmation via HDS,
the following information has now been obtained, that helps to clarify the intended
use of the noread argument, and in which pair state the "noread" functionality applies.

The ShadowImage -m noread option only applies to the S-VOL, when the ShadowImage pair are in a *PAIR* or *COPY* status.

S-VOL STATUS with -m noread without -m noread
------------ --------------- -----------------
PAIR no access read only
COPY no access read only
SSUS read/write read/write

The purpose of the -m noread argument is to prevent users from backing up (reading) the S-VOL, while it is still linked (paired) to the primary volume (P-VOL), and therefore still changing.


-- End --

I think the abridged version that I have suggested may be more suited for submission
as a Knowledge Article (KA) ?If you are in agreement, please re-submit this KA with my
suggested ammendements, and I wil be pleased to re-review it. If not, then please
advise.

Note: I will be submitting a RFE requesting that the CCI documentation is improved
reference the descrition/explanation of the SI -m noread option. So once
those changes are implemented, this KA will immediately become obsolete and not
required.
Version: 0
Date: 2004-11-24
User Name: 26313
Action: Accept
Comment:
Version: 0
Date: 2004-11-23
User Name: 128938
Action: Approved
Comment: Some useful (in my opionio) HDS Shadowimage command option for technical review.
Version: 0
Date: 2004-11-23
User Name: 128938
Action: Created
Comment:
Version: 0
Product_uuid
f55c65ae-16a0-11d7-82ad-99701a4c6e31|Sun StorageTek 9900V Series Array
2a918ae2-0a18-11d6-834a-c679537eebe7|Sun StorageTek 9910
2a94fb3c-0a18-11d6-90a8-c9c08656284f|Sun StorageTek 9960 System
15644879-f179-11d8-ab63-080020a9ed93|Sun StorageTek 9990 System

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