CONTENT-BASED REPLICATION OF DATA IN SCALE OUT SYSTEM

• US 20160147855A1
• Filed: 11/24/2015
• Published: 05/26/2016
• Est. Priority Date: 11/25/2014
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Nimble Storage (Hewlett-Packard Enterprise Company)
• Inventors: Bhagat, Nimesh, Barszczak, Tomasz, Karaje, Gurunatha
• Granted Patent: US 10,467,246 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1844 Management specifically adapted to replicated file systems
• CPC Class Codes: G06F 16/2237 Vectors, bitmaps or matrices
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

Methods, systems, and programs are presented for replicating data across scale-out storage systems. One method includes replicating, from an upstream to a downstream system, a volume snapshot having one or more bins. Locations for the bins of the snapshot are identified, the location for each bin including the upstream array storing the bin and the downstream array storing a replicated version of the bin. Each bin is validated by comparing an upstream bin checksum of the bin with a downstream bin checksum of the replicated version of the bin. When the checksums are different, a plurality of chunks are defined in the bin, and for each chunk in the bin an upstream chunk checksum calculated by the upstream array is compared with a downstream chunk checksum calculated by the downstream array. The chunk is sent from the upstream to the downstream array when the chunk checksums are different.

Claims

1. A method for replicating data across storage systems, the method comprising:

replicating a snapshot of a volume from an upstream system to a downstream system, the volume being a predefined logical storage area, the snapshot including one or more bins, the upstream system including one or more upstream arrays and the downstream system including one or more downstream arrays;

identifying locations for the bins of the snapshot, the location for each bin including the upstream array storing the bin and the downstream array storing a replicated version of the bin;

validating each bin by comparing an upstream bin checksum of the bin calculated by the corresponding upstream array with a downstream bin checksum of the replicated version of the bin calculated by the corresponding downstream array;

when the upstream bin checksum is different from the downstream bin checksum, defining a plurality of chunks in the bin; and

for each chunk in the bin,

comparing an upstream chunk checksum calculated by the upstream array with a downstream chunk checksum calculated by the downstream array; and

sending, from the upstream array to the downstream array, data of the chunk when the upstream chunk checksum is different from the downstream chunk checksum.

2. The method as recited in claim 1, wherein data of the volume is striped across the one or more bins, wherein a unit for striping the volume is a slice, wherein each bin includes one or more slices, wherein each slice includes one or more chunks, and wherein each chunk includes one or more blocks.

3. The method as recited in claim 1, further including:

exchanging, before defining the plurality of chunks, transfer parameters between the upstream array and the downstream array for the corresponding bin, the transfer parameters including one or more of checksum type for calculating the upstream chunk checksum and the downstream chunk checksum, or a checksum size, or a chunk size, or a cursor indicating at what chunk to start the comparing of the upstream chunk checksum and the downstream chunk checksum.

4. The method as recited in claim 3, further including:

starting comparing the upstream chunk checksum with the downstream chunk checksum at the chunk indicated by the cursor.

5. The method as recited in claim 1, wherein comparing the upstream chunk checksum with the downstream chunk checksum further includes:

calculating, by the upstream array, the upstream chunk checksum;

sending, from the upstream array to the downstream array, a request to get the downstream chunk checksum;

calculating, by the downstream array, the downstream chunk checksum;

sending the downstream chunk checksum to the upstream array; and

comparing, by the upstream array, the upstream chunk checksum with the downstream chunk checksum.

6. The method as recited in claim 1, wherein replicating the snapshot further includes:

for each upstream array having one or more bins of the snapshot,

identifying, for each bin in the upstream array, a corresponding downstream array to store the replicated version of the bin; and

transferring all data of each bin from the upstream array to the corresponding downstream array.

7. The method as recited in claim 1, wherein each upstream array is a first storage system that includes a first processor, a first volatile memory, and a first permanent storage, wherein each downstream array is a second storage system that includes a second processor, a second volatile memory, and a second permanent storage, wherein a volume holds data for a single accessible storage area, wherein data of the volume is accessible by a host in communication with the storage system.

8. The method as recited in claim 1, further including:

after sending data of the chunk from the upstream array to the downstream array, sending, from the upstream array to the downstream array, a confirmation message indicating that the chunk has been validated; and

after validating all chunks in the bin, sending, from the upstream array to the downstream array, a confirmation message indicating that the bin has been validated.

9. The method as recited in claim 1,wherein the snapshot of the volume includes one or more blocks, wherein data from the snapshot is accessed by a host in units of a size of the block, the method further including:

storing, in the upstream array, checksums of blocks of the snapshot; and

calculating the upstream chunk checksum based on the checksums of the blocks in the chunk, wherein the chunk is not uncompressed to calculate the upstream chunk checksum.

10. The method as recited in claim 9, wherein a chunk includes one hundred or more blocks, wherein data from the chunk is not directly addressable by the host.

11. The method as recited in claim 9, wherein a chunk has a size in a range from 1 Megabyte to 32 Megabytes, wherein a block has a block size in a range from 1 Kilobyte to 256 Kilobytes, wherein a slice has a size in a range from 2 Megabytes to 100 Megabytes.

12. A method for replicating data across storage systems, the method comprising:

replicating a snapshot of a volume from an upstream system to a downstream system, the volume being a predefined logical storage area, the snapshot including one or more bins, each bin including one or more slices, the upstream system including one or more upstream arrays and the downstream system including one or more downstream arrays;

identifying locations for the bins of the snapshot, the location for each bin including the upstream array storing the bin and the downstream array storing a replicated version of the bin;

validating each bin by comparing an upstream bin checksum of the bin calculated by the corresponding upstream array with a downstream bin checksum of the replicated version of the bin calculated by the corresponding downstream array; and

when the upstream bin checksum is different from the downstream bin checksum, for each slice in the bin,

comparing an upstream slice checksum calculated by the upstream array with a downstream slice checksum calculated by the downstream array;

when the upstream slice checksum is different from the downstream slice checksum, defining a plurality of chunks in the slice; and

for each chunk in the slice,

comparing an upstream chunk checksum calculated by the upstream array with a downstream chunk checksum calculated by the downstream array; and

sending, from the upstream array to the downstream array, data of the chunk when the upstream chunk checksum is different from the downstream chunk checksum.

13. The method as recited in claim 12, wherein data of the volume is striped across the one or more bins, wherein a unit for striping the volume is the slice, wherein each chunk includes one or more blocks.

14. The method as recited in claim 12, further including:

exchanging transfer parameters between the upstream array and the downstream array for the corresponding bin, the transfer parameters including one or more of checksum type for calculating the upstream chunk checksum and the downstream chunk checksum, or a checksum size, or a chunk size, or a cursor indicating at what chunk to start the comparing of the upstream chunk checksum and the downstream chunk checksum.

15. The method as recited in claim 12, wherein data from the snapshot is accessed by a host in units of a size of a block, the method further including:

storing, in the upstream array, checksums of blocks of the snapshot; and

calculating the upstream chunk checksum based on the checksums of the blocks in the chunk, wherein the chunk is not uncompressed to calculate the upstream chunk checksum.

16. The method as recited in claim 12, wherein operations of the method are performed by a computer program when executed by one or more processors, the computer program being embedded in a non-transitory computer-readable storage medium.

17. A non-transitory computer-readable storage medium storing a computer program for replicating data across storage systems, the computer-readable storage medium comprising:

program instructions for replicating a snapshot of a volume from an upstream system to a downstream system, the volume being a predefined logical storage area, the snapshot including one or more bins, the upstream system including one or more upstream arrays and the downstream system including one or more downstream arrays;

program instructions for identifying locations for the bins of the snapshot, the location for each bin including the upstream array storing the bin and the downstream array storing a replicated version of the bin;

program instructions for validating each bin by comparing an upstream bin checksum of the bin calculated by the corresponding upstream array with a downstream bin checksum of the replicated version of the bin calculated by the corresponding downstream array;

program instructions for defining a plurality of chunks in the bin when the upstream bin checksum is different from the downstream bin checksum; and

for each chunk in the bin,

program instructions for comparing an upstream chunk checksum calculated by the upstream array with a downstream chunk checksum calculated by the downstream array; and

program instructions for sending, from the upstream array to the downstream array, data of the chunk when the upstream chunk checksum is different from the downstream chunk checksum.

18. The storage medium as recited in claim 17, wherein data of the volume is striped across the one or more bins, wherein a unit for striping the volume is a slice, wherein each bin includes one or more slices, wherein each slice includes one or more chunks, and wherein each chunk includes one or more blocks.

19. The storage medium as recited in claim 17, further including:

program instructions for exchanging, before defining the plurality of chunks, transfer parameters between the upstream array and the downstream array for the corresponding bin, the transfer parameters including one or more of checksum type for calculating the upstream chunk checksum and the downstream chunk checksum, or a checksum size, or a chunk size, or a cursor indicating at what chunk to start the comparing of the upstream chunk checksum and the downstream chunk checksum.

20. The storage medium as recited in claim 17, further including:

program instructions for sending from the upstream array to the downstream array, after sending data of the chunk from the upstream array to the downstream array, a confirmation message indicating that the chunk has been validated; and

program instructions for sending from the upstream array to the downstream array, after validating all chunks in the bin, a confirmation message indicating that the bin has been validated.