Specifications

Owned by SungEun Kim
Last updated: 2024/03/21
5 min read

Environments

The following are the platforms supported by FSR and the physical requirements of the target system.


Platforms

Works on Windows 2012 x64 or later, Linux CentOS 6.4, and Ubuntu 16.04 LTS x64 or later. Filesystems support NTFS, ReFS and the ext family (ext3 and later), and xfs. (Older filesystems, such as the FAT family, are not supported).

CPU

Works with at least 2GHz, 4 core or higher x86/x64 compatible processor.

Memory


system memory

It is recommended that the system have at least 4GB of memory and at least 30% of the physical memory usage as free space. Typically, the point at which the operating system starts paging to respond to memory shortage is considered to be when physical memory usage exceeds 70%. When paging is enabled in the system, overall I/O performance may decrease, so this must be taken into consideration.

memory buffer size

The memory buffer for replication is used to buffer the local I/O load, and its size is obtained by the following equation.

Size of maximum bandwidth transmitted per time (seconds) * timeout time (seconds)
In the case of 1Gbps, you can obtain approximately 100MB/s * 5s = 500MB, and you can configure it at the level of 500MB to 1GB with more room than 500MB.

If the variable band of the WAN section needs to be considered for DR configuration, WAN bottleneck situation is responded to with DRX buffering through DRX linkage. If DRX is not linked, allocate a larger memory buffer size as described above (2 to 3 times the memory buffer), and if there is no available memory space, consider configuring it as a file buffer (see below).

However, when WAN replication (DR) is configured, if the size of the memory buffer is configured to be too large compared to the size of the band, the data accumulated in the buffer itself may act as a bottleneck, which may intensify delay (buffer bloat). Tuning may be necessary to lower the large buffer size and adjust it to an appropriate level.

Disk

  • Approximately 2GB is required for basic installation, including installation files, engine files, and performance logs.
  • An additional 110 MB per resource is required for debug file logs.
  • If you configure a file buffer, you will need disk space equal to the size of the file buffer.

file buffer

File buffer is a function that allows you to use regular files as a buffer. However, using a file buffer may result in performance degradation compared to existing local I/O. To minimize performance degradation, it is recommended to configure a dedicated disk volume for the file buffer.

The file buffer can be sized to suit the user's purpose, and the size is usually set at 5 to 10 times the size of the memory buffer.


Functional scope

Replications of some system files is excluded. This is a description of the specific range of functions supported by fsr.


Disk Path

You can replicate the path of a regular local disk. Remote paths such as NFS cannot be replicated (NFS paths only support source operation for periodic synchronization).


File Types

The following file types are supported.

  • general files and directories
  • link files
    • soft link
    • hard link
    • junction, reparse point
  • sparse file
  • compressed file
  • encrypted file
  • special file
    • NTFS ADS(Alternate Data Stream)
    • NTFS TxF(Transaction File)

Be careful not to specify system files used by the OS as replication targets. Duplicating system files may cause unexpected problems, such as replication competing with system I/O. This includes system files, driver files, swap files, OS installation path (Windows path), etc.

  • A link file is a file that points to another path. If the link file within the replication target points to an external path outside of the replication path, fsr replicates the link file itself, but does not replicate the destination pointed to by the link. This is because the path pointed to by the link file is not the replication target path registered in fsr. Therefore, if you want to duplicate the path pointed to by the link file, we recommend that you register and configure the path pointed to by the link as a direct replication path.
  • Hard links linking one file may exist inside and outside the replication path. In this case, changes to hardlinks on external paths that are not the target of replication cannot be tracked by fsr, so replication from the perspective of hardlinks located on paths inside replication may be missed. Therefore, when configuring replication, it is necessary to determine in advance whether hard links are linking inside or outside the replication path.


I/O Types

Most of the I/O types supported by Windows and Linux are supported.

  • General I/O
    • Buffered I/O(Cached I/O)
    • Direct I/O(Non-Cached I/O)
  • Memory Mapped I/O
  • Special I/O
    • linux
      • Async I/O(aio)
      • Vector Write(writev)
      • Splice I/O
      • Uring I/O

Splice I/O in Linux is a special I/O that implements zero copy for high-speed data transfer. FSR can capture and replicate Splice I/O, but additional Copy Latency is required in the process of copying Splice I/O data for replication, resulting in performance degradation compared to original Splice I/O. This is an unavoidable technical limitation of implementing data replication. You should take this into account when replicating data from applications that use Splice I/O.


File Properties

Replicate the following file attributes.

  • File properties: read-only, hidden, system, directory, archive, sparse, compressed, encrypted
  • ACL: SID or account name of the source file
  • Time: modification time

It replicates most of the file attributes, but the file time attribute is only replicated for the modification time and not for other times. For example, it is technically impossible to match the file access times of the source and target.

  • Among the file attributes in Windows, the device attribute (FILE_ATTRIBUTE_DEVICE) and virtual attribute (FILE_ATTRIBUTE_VIRTUAL) are system-reserved attributes and are excluded from replication.
  • The following file attributes related to OneDrive added in Windows 10 are not supported.
    • FILE_ATTRIBUTE_RECALL_ON_OPEN
    • FILE_ATTRIBUTE_PINNED
    • FILE_ATTRIBUTE_UNPINNED
    • FILE_ATTRIBUTE_RECALL_ON_DATA_ACCESS

For HA operation, the principle is to configure the source and target systems with the same security account status. However, it is realistically difficult to configure the security configuration of the source and target systems to be completely identical and may not conform to the customer's security policy. Even if the security configuration status of the source and target are different, FSR replicates files based on the security identifier (SID) of the files on the source side to ensure that there are at least no problems with the replication operation. Afterwards, in order to access the copied files in the target, follow-up measures, such as adjusting the target's account and permissions, must be followed.



Operation Method

  • It is based on active-passive clustering operation.
  • Supports one-way replication from primary to secondary nodes. Operating methods such as circular mirroring and dual primary mode are not supported.
  • Asynchronous replication is supported, but synchronous replication is not supported.