D-Link DSN-6210 User Manual - Page 114

keeps growing. When it comes to the moment when the snapshot space has run out, the system

Get D-Link DSN-6210 PDF manuals and user guides View all D-Link DSN-6210 manuals
Add to My Manuals
Save this manual to your list of manuals

Page 114 highlights

D-Link Document - User Manual On Linux and UNIX platform, a command named sync can be used to make the operating system flush data from write caching into disk. For Windows platform, Microsoft also provides a tool - sync, which can do exactly the same thing as the sync command in Linux/UNIX. It will tell the OS to flush the data on demand. For more detail about sync tool, please refer to: http://technet.microsoft.com/en-us/sysinternals/bb897438.aspx Besides the sync tool, Microsoft develops VSS (volume shadow copy service) to prevent this issue. VSS is a mechanism for creating consistent point-in-time copies of data known as shadow copies. It is a coordinator between backup software, application (SQL or Exchange...) and storage to make sure the snapshot doesn't have the problem of data-inconsistencies. For more detail about the VSS, please refer to http://technet.microsoft.com/en-us/library/cc785914.aspx. The DSN6200/6500 storage system can support Microsoft VSS.  What if there is not enough snapshot space? Before using snapshot, a snapshot space is needed from RAID group capacity. After a period of working snapshot, what if the snapshot size is over the snapshot space defined by the user? There are two different situations: 1. If there are two or more snapshots existing, the system will try to remove the oldest of snapshots (to release more space for the latest snapshot) until enough space is released. 2. If there is only one snapshot, the snapshot will fail. Because there isn't enough snapshot space. For example, if there are two or more snapshots existing on a virtual disk and the latest snapshot keeps growing. When it comes to the moment when the snapshot space has run out, the system will try to remove the oldest snapshot to release more space for the latest snapshot usage. As the latest snapshot is growing, the system keeps removing the old snapshots. When it comes that the latest snapshot is the only one in the system, there is no more snapshot space which can be released for incoming changes, then the snapshot will fail.  How many snapshots can be created on a virtual disk? There are up to 64 snapshots can be created per virtual disk. What if the 65th snapshot has been taken? There are two different situations: 1. If the snapshot is configured as a schedule snapshot, the latest one (the 65th snapshot) will replace the oldest one (the first snapshot) and so on. 2. If the snapshot is taken manually, when taking the 65th snapshot it will fail and a warning message will be shown on the Web UI. Copyright@2014 D-Link System, Inc. All Rights Reserved. 114

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
  • 134
  • 135
  • 136
  • 137
  • 138
  • 139
  • 140
  • 141
  • 142
  • 143
  • 144
  • 145
  • 146
  • 147
  • 148
  • 149
  • 150
  • 151
  • 152
  • 153
  • 154
  • 155
D-Link Document – User Manual
On Linux and UNIX platform, a command named
sync
can be used to make the operating system
flush data from write caching into disk. For Windows platform, Microsoft also provides a tool –
sync
, which can do exactly the same thing as the
sync
command in Linux/UNIX. It will tell the OS to
flush the data on demand. For more detail about
sync
tool, please refer to:
Besides the
sync
tool, Microsoft develops
VSS
(volume shadow copy service) to prevent this issue.
VSS is a mechanism for creating consistent point-in-time copies of data known as shadow copies. It
is a coordinator between backup software, application (SQL or Exchange…) and storage to make
sure the snapshot doesn’t have the problem of data-inconsistencies. For more detail about the
VSS, please refer to
The DSN-
6200/6500 storage system can support Microsoft VSS.
What if there is not enough snapshot space?
Before using snapshot, a snapshot space is needed from RAID group capacity. After a period of
working snapshot, what if the snapshot size is over the snapshot space defined by the user? There
are two different situations:
1.
If there are two or more snapshots existing, the system will try to remove the oldest of
snapshots (to release more space for the latest snapshot) until enough space is
released.
2.
If there is only one snapshot, the snapshot will fail. Because there isn’t enough
snapshot space.
For example, if there are two or more snapshots existing on a virtual disk and the latest snapshot
keeps growing. When it comes to the moment when the snapshot space has run out, the system
will try to remove the oldest snapshot to release more space for the latest snapshot usage. As the
latest snapshot is growing, the system keeps removing the old snapshots. When it comes that the
latest snapshot is the only one in the system, there is no more snapshot space which can be
released for incoming changes, then the snapshot will fail.
How many snapshots can be created on a virtual disk?
There are up to 64 snapshots can be created per virtual disk. What if the 65th snapshot has been
taken? There are two different situations:
1.
If the snapshot is configured as a schedule snapshot, the latest one (the 65th
snapshot) will replace the oldest one (the first snapshot) and so on.
2.
If the snapshot is taken manually, when taking the 65th snapshot it will fail and a
warning message will be shown on the Web UI.
114
Copyright@2014 D-Link System, Inc. All Rights Reserved.