Upgrading On-Disk Format Without Service Interruption

Patent metadata

Field	Value
Publication number	US-2022019528-A1
Application number	US-202016933162-A
Country	US
Kind code	A1
Filing date	Jul 20, 2020
Priority date	Jul 20, 2020
Publication date	Jan 20, 2022
Grant date	—

Abstract

A logical map represents fragments from separate versions of a data object. Migration of data from a first (old) version to the second (new) version happens gradually, where write operations go to the new version of the data object. The logical map initially points to the old data object, but is updated to point to the portions of the new data object as write operations are performed on the new data object. A background migration copies data from the old data object to the new data object.

First claim

1 . A method comprising:
receiving a read operation to read data from a data object; accessing a plurality of map entries stored in a logical map, the logical map representing fragments of a first version of the data object and fragments of a second version of the data object, each map entry including a flag that is set to indicate whether a fragment is the first version of the data object or the fragment is the second version of the data object; and reading data from each fragment represented by each of the plurality of accessed map entries including: when said each accessed map entry includes the flag that is set to indicate a fragment is the first version of the data object, then reading the data from the first version of the data object; and when said each accessed map entry includes the flag that is set to indicate a fragment is the second version of the data object, then reading the data from the second version of the data object.

2 . The method of claim 1 , wherein the received read operation specifies a starting logical block L in the data object, the method including:
accessing a first map entry from the logical map that represents a fragment containing the starting logical block L; and reading a portion of data contained the fragment determined based on a location of the starting logical block within the fragment.

3 . The method of claim 2 , wherein reading a portion of data contained the fragment is further determined based on a remaining number of blocks of the read operation.

4 . The method of claim 1 , wherein a fragment of the first version of the data object comprises one or more logical blocks of the data object that are stored in the first version of the data object, wherein a fragment of the second version of the data object comprises one or more logical blocks of the data object that are stored in the second version of the data object.

5 . The method of claim 1 , wherein each map entry in the logical map comprises a logical block address (LBA) of a first logical block in the fragment represented by said each map entry and a block count of the number of blocks in the fragment, wherein accessing the map entry includes searching the plurality of map entries in the logical map for a map entry having the largest logical block address that is equal to or less than the starting block L.

6 . The method of claim 1 , wherein reading data from the first or second version of the data object includes accessing one or more physical data blocks on a respective data storage device of the first or second version of the data object and using physical block address (PBA) information in the accessed map entry to access the one or more physical data blocks on the respective data storage device.

7 . The method of claim 1 , wherein the first version of the data object is a virtual disk having a first storage format, wherein the second version of the data object is virtual disk having a second storage format different from the first storage format.

8 . A non-transitory computer-readable storage medium having stored thereon computer executable instructions, which when executed by a computer device, cause the computer device to:
receive a read operation to read data from a data object; access a plurality of map entries stored in a logical map, the logical map representing fragments of a first version of the data object and fragments of a second version of the data object, each map entry including a flag that is set to indicate whether a fragment is the first version of the data object or the fragment is the second version of the data object; and read data from each fragment represented by each of the plurality of accessed map entries including:
when said each accessed map entry includes the flag that is set to indicate a fragment is the first version of the data object, then reading the data from the first version of the data object; and
when said each accessed map entry includes the flag that is set to indicate a fragment is the second version of the data object, then reading the data from the second version of the data object.

9 . The non-transitory computer-readable storage medium of claim 8 , wherein the read operation specifies a starting logical block L in the data object, the method including:
accessing a first map entry from the logical map that represents a fragment containing the starting logical block L; and reading a portion of data contained the fragment determined based on a location of the starting logical block within the fragment.

10 . The non-transitory computer-readable storage medium of claim 9 , wherein reading a portion of data contained the fragment is further determined based on a remaining number of blocks of the read operation.

11 . The non-transitory computer-readable storage medium of claim 8 , wherein a fragment of the first version of the data object comprises one or more logical blocks of the data object that are stored in the first version of the data object, wherein a fragment of the second version of the data object comprises one or more logical blocks of the data object that are stored in the second version of the data object.

12 . The non-transitory computer-readable storage medium of claim 8 , wherein each map entry in the logical map comprises a logical block address (LBA) of a first logical block in the fragment represented by said each map entry and a block count of the number of blocks in the fragment, wherein accessing the map entry includes searching the plurality of map entries in the logical map for a map entry having the largest logical block address that is equal to or less than the starting block L.

14 . The non-transitory computer-readable storage medium of claim 8 , wherein reading data from the first or second version of the data object includes accessing one or more physical data blocks on a respective data storage device of the first or second version of the data object and using physical block address (PBA) information in the accessed map entry to access the one or more physical data blocks on the respective data storage device.

15 . The non-transitory computer-readable storage medium of claim 8 , wherein the first version of the data object is a virtual disk having a first storage format, wherein the second version of the data object is virtual disk having a second storage format different from the first storage format.

16 . An apparatus comprising:
one or more computer processors; and a non-transitory computer-readable storage medium comprising instructions for controlling the one or more computer processors to: receive a read operation to read data from a data object; access a plurality of map entries stored in a logical map, the logical map representing fragments of a first version of the data object and fragments of a second version of the data object, each map entry including a flag that is set to indicate whether a fragment is the first version of the data object or the fragment is the second version of the data object; and read data from each fragment represented by each of the plurality of accessed map entries including: when said each accessed map entry includes the flag that is set to indicate a fragment is the first version of the data object, then read the data from the first version of the data object; and when said each accessed map entry includes the flag that is set to indicate a fragment is the second version of the data object, then read the data from the second version of the data object.

17 . The apparatus of claim 15 , wherein the read operation specifies a starting logical block L in the data ob

Assignees

• Vmware Inc

Inventors

• Wang Wenguang
• Gunturu Vamsi

Classifications

• G06F3/064

  Management of blocks · CPC title

• G06F3/0617 Primary

  in relation to availability · CPC title

• G06F3/0661

  Format or protocol conversion arrangements · CPC title

• G06F3/0674

  Disk device · CPC title

• G06F3/067

  Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS] · CPC title