Got it

Classification of Differential Snapshots(COW and ROW)

Latest reply: May 5, 2022 06:02:28 714 32 17 0 0

Snapshot:

Snapshot is a point-in-time copy implementation that saves the state of data at a certain point in time. By combining copy-on-write technology and mapping table technology, Snapshot creates a duplicate of the source LUNs at a certain point, rather than a complete physical data copy. Users can use snapshot technology to create recovery points for stored data flexibly and regularly, allowing for quick data recovery when needed.

Classification of Snapshots:

There are two types of snapshots first is full snapshots and the other is Differential or incremental snapshots. So when we go deeper the further classification includes ROW and COW.

Copy-on-write (COW) and Redirect-on-write (ROW) are two different types of Differential snapshot

Now let's have a detailed description of these two

COW:

Copy-on-write needs the provisioning of storage capacity for snapshots, followed by the creation of a volume snapshot utilizing the reserved capacity. The metadata indicating where the original data is located is stored in the copy-on-write snapshot, but the actual data is not copied at the time of generation. As a result, snapshot production is nearly immediate, with minimal impact on the machine that is taking the picture.

Each snapshot includes metadata that describes the data blocks that have changed since it was produced. The original data is replicated into the reserved storage capacity set aside for the snapshot as the blocks change. Read requests for data that hasn't changed are sent to the original volume. The procedure is known as "copy-on-write," and it is the reason for its widespread use.

Write requests to the original volume must wait until the original data is "copied out" to the snapshot, which is a disadvantage. Before a snapshot can be stored, it must have a valid original copy of the data that has changed.

 

ROW: 

Redirect-on-write is related to copy-on-write, except it avoids the performance cost of a double write. ROW also offers storage-saving snapshots, such as copy-on-write. The new writes to the original volume are diverted to the storage allotted for snapshots, which allows ROW to avoid the write performance penalty. The number of new writes is reduced from two to one by using ROW redirection. Instead of writing one copy of the original data plus a copy of the altered data to the storage space as required by COW, ROW writes only the changed data.

When using redirect-on-write, the original copy contains the point-in-time snapshot data, while the altered data is saved to the snapshot storage. The point-in-time snapshot data is stored in the original copy with redirect-on-write. When a picture is erased, there's some complication. On the original volume, the data from the deleted snapshot must be duplicated and made consistent. As additional snapshots are created, the complexity rises dramatically.

Conclusion:

they both have their application scenarios but Before writing the new data in the original location, COW copies the old value to a separate section in the snapshot. This indicates that a file will remain continuous. ROW saves the original data in the snapshot while writing to a new region. This saves the copy, making it faster, but also creates non-contiguous files. As a result, COW is better suited to read-intensive applications or apps that are prone to write hotspots, or applications that only write data to a small set of data. Multiple write operations to the same data will only result in one replication operation since data changes are confined to a range. ROW is better for applications that require a lot of writing. In the event of distributed storage, ROW will outperform COW in terms of read performance.

 

Sources and references:

https://support.huawei.com/enterprise/en/doc/EDOC1100200561

https://support.huawei.com/enterprise/en/doc/EDOC1100049150/2e33469b/about-snapshots

https://www.techtarget.com/searchdatabackup/tip/Using-different-types-of-storage-snapshot-technologies-for-data-protection

 

 

 

 


  • x
  • convention:

MahMush
Moderator Author Created Mar 17, 2022 05:08:46

  • x
  • convention:

Saqibaz
Saqibaz Created Mar 17, 2022 05:29:54 (0) (0)
 
Saqibaz
Created Mar 17, 2022 05:30:11

Thanks for sharing
View more
  • x
  • convention:

MahMush
MahMush Created Mar 18, 2022 04:32:45 (0) (0)
hope you get something new  
Funstuff
Moderator Author Created Mar 17, 2022 06:06:57

Great share. well described the classifications of snapshots
View more
  • x
  • convention:

MahMush
MahMush Created Mar 18, 2022 04:33:04 (0) (0)
glad to know it  
MahMush
MahMush Created Mar 18, 2022 04:33:58 (0) (0)
hope you get something new from it  
taha_29four
Created Mar 17, 2022 06:25:28

Simple and good explanation, nice :)
View more
  • x
  • convention:

MahMush
MahMush Created Mar 18, 2022 04:33:21 (0) (0)
happy to hear it  
MahMush
MahMush Created Mar 18, 2022 04:33:45 (0) (0)
thanks for your support  
Abdussamed
HCIE MVE Created Mar 17, 2022 07:34:04

Thanks for sharing
View more
  • x
  • convention:

MahMush
MahMush Created Mar 20, 2022 04:33:29 (0) (0)
thanks to revie it  
zaheernew
MVE Author Created Mar 17, 2022 12:51:05

very clear conclusion.
View more
  • x
  • convention:

MahMush
MahMush Created Mar 18, 2022 04:35:44 (0) (0)
thanks for your time  
Anno7
Moderator Author Created Mar 20, 2022 04:34:23

great explanation
View more
  • x
  • convention:

MahMush
MahMush Created Mar 21, 2022 05:03:25 (0) (0)
thanks for response please share some thoughts on it  
manpham
Created Mar 20, 2022 10:13:44

Good share
View more
  • x
  • convention:

MahMush
MahMush Created Mar 21, 2022 05:03:36 (0) (0)
glad to know it  
user_4358465
Created Mar 25, 2022 10:20:48

Great share on the classifications of snapshots
View more
  • x
  • convention:

MahMush
MahMush Created Mar 30, 2022 06:57:13 (0) (0)
thanks for your support  
12
Back to list

Comment

You need to log in to comment to the post Login | Register
Comment

Notice: To protect the legitimate rights and interests of you, the community, and third parties, do not release content that may bring legal risks to all parties, including but are not limited to the following:
  • Politically sensitive content
  • Content concerning pornography, gambling, and drug abuse
  • Content that may disclose or infringe upon others ' commercial secrets, intellectual properties, including trade marks, copyrights, and patents, and personal privacy
Do not share your account and password with others. All operations performed using your account will be regarded as your own actions and all consequences arising therefrom will be borne by you. For details, see " User Agreement."

My Followers

Login and enjoy all the member benefits

Login

Block
Are you sure to block this user?
Users on your blacklist cannot comment on your post,cannot mention you, cannot send you private messages.
Reminder
Please bind your phone number to obtain invitation bonus.
Information Protection Guide
Thanks for using Huawei Enterprise Support Community! We will help you learn how we collect, use, store and share your personal information and the rights you have in accordance with Privacy Policy and User Agreement.