This post is more than 5 years old
1 Rookie
•
35 Posts
0
2188
January 5th, 2013 23:00
will reversed lun pool be full after fractured in mirrorview/A
I want to know what RLP status is in PR site VNX after the mirror’s secondary image is fractured. Will it be possible full since the data can not transmit to the DR site?
No Events found!
Storagesavvy
474 Posts
0
January 6th, 2013 10:00
MV/A uses Snapview snapshot technology to ensure consistency at the DR location. For normal Snapview Snapshots, the RLP will continue to grow as long as there is a snapshot session. Only when a snapshot session is destroyed, the space consumed in the RLP for that session is released.
For Mirrorview/A, the use of the RLP is different from a snapshot. The RLP stores a bitmap in each RLP and that remains even with the MV/A session is fractured. But the bitmaps are very small and do not grow. The bitmap just tracks which blocks in the LUN have been modified at least once since the last MV/A update. COFW data is only created/tracked during an active update. When an update starts, MV/A checks the bitmap and creates a snapshot session for only the blocks that are marked for the update. Then during the update, any writes to a marked block create COFW data which is stored in the RLP. When the update completes successfully, the bitmap and COFW data are both cleared. If an update is unsuccessful and the session fractures, the bitmap remains, ready for another attempt, but the snapshot session is removed and the COFW data is cleared.
Technically there are two bitmaps per source LUN. One is used between updates to mark changes, and the other is used to mark new changes while the update is in progress. The bitmaps swap each time an update starts.
Compared to a full snapshot, MV/A creates less COFW data and has a lower performance impact on the source LUN.
I hope that makes sense.
Richard J Anderson
AnkitMehta
1.4K Posts
1
January 5th, 2013 23:00
Nope, RLP will not be full until you synchronize the mirror.
Explanation:
RLP consists of one or more private LUNs. You cannot assign a private LUN to a storage group; therefore, a server cannot perform I/O to it. A LUN becomes private when you add it to the reserved LUN pool.
However, The LUN resources of the reserved LUN pool are shared across Navisphere applications, such as SnapView and MirrorView/A. The LUN pool must contain at least one LUN for each source LUN that will participate in a SnapView or MirrorView/A session. For example, if you run a MirrorView/A session on one LUN and a snapshot session on another LUN and both source LUNs belong to the same SP, the reserved LUN pool for that SP must contain at least two LUNs - one for each source LUN.
rickyjj
1 Rookie
•
35 Posts
0
January 6th, 2013 00:00
Thanks for your answer.
Since the knowledgebook said “reserved luns on the primary side are used for storing the bitmaps associated with delta sets and for storing any COFW data that is created during the update”. At the beginning, I worried whether RLP will continue to be written in until it increases full after secondary image fractured.
So I did the test for this . The result is that the RLP capacity doesn't seem have any increase after I fracture the secondary image.
Will the bitmap continue to track and consume little the RLP space after fracture ？ Could it incremental transmit when I synchronize the mirror again？
AnkitMehta
1.4K Posts
0
January 6th, 2013 03:00
Yes, in the Primary Storage System. Once, you are re-synchronizing you are actually doing an incremental update (if Initial Sync is completed).
AnkitMehta
1.4K Posts
0
January 6th, 2013 10:00
Yupp, I am well aware of emded EMC SANCopy and Snapview Snapshot in Mirrorview/A
Hence, my I mentioned: Yes, in the Primary Storage System.
rickyjj
1 Rookie
•
35 Posts
0
January 6th, 2013 21:00
It’s very helpful, many thanks!
****************************************************
Junjie Huang(黄君杰)
Implementation Delivery Specialist
EMC Shenzhen
MP:13828737272
Email:ricky.huang@emc.com
EMC 24-hour Mandarin Support Line: 8008190009 / 4006700009
发件人: Richard Anderson
发送时间: 2013年1月7日 2:41
收件人: Huang, Ricky
主题: New message: "will reversed lun pool be full after fractured in mirrorview/A"
EMC Community Network
Re: will reversed lun pool be full after fractured in mirrorview/A
created by Richard Anderson in CLARiiON Support Forum - View the full discussion