StorView RAID Module
198
If the Overwrite Data Area storage space gets close to running out of storage space, it will alert the user.
If the Overwrite Data Area does get filled to its limit and can no longer store copy-on-write data, the
Snapshot will become out of phase with the underlying snapshotted logical drive resulting in all
Snapshots for this logical drive being invalidated by the RAID Controller.
C.6 ODA Assignment
Each logical drive can be snapshotted up to 24 times. Each one of these 24 snapshots represents a full
virtual copy of the snapshotted logical drive at the point in time of the snapshot.
Before snapshots can be issued on a logical drive an ODA area must be assigned for its use. Once the
ODA has been assigned it will remain assigned as long as it is needed.
C.7 Snapshots and Caching
It is of the highest importance that disk data caching be handled properly when using the RAID Controller
snapshot engine.
The purpose of a snapshot is to generate a point-in-time reference marker that allows a system
administrator restoration of a logical drive data to the state it was at the time the snapshot was taken. Due
to disk data caching, it is required to keep track of the status of the various caches present in the server
installation environment. A server might believe a block of data has been committed to the disk when it
is actually kept waiting in the RAID Controller cache. Likewise, an application such as a database might
believe its data has been saved on the disk but in reality the data still resides in the server OS cache and
has not yet been sent to the disk array.
C.7.1 Application Caches
Advanced applications, such as databases, might implement their own data cache to speed up execution.
Before a snapshot can be issued this application cached data must be flushed. If the application does not
provide a means to flush its cache, close down the application before the snapshot is issued.
Refer to your application user documentation for more information.
Table C–1
Available ODA Stripe Sizes
ODA Stripe Size
ODA Storage Capacity
64 Kbytes
512 GBs
128 Kbytes
1 Terabyte
256 Kbytes
2 Terabytes
512 Kbytes
4 Terabytes
1 Mbyte
8 Terabytes
Summary of Contents for 131018 - StorView Snapshot - Mac
Page 28: ...StorView RAID Module 20...
Page 34: ...StorView RAID Module 26...
Page 76: ...StorView RAID Module 68...
Page 79: ...SAN LUN Mapping 71 Figure 7 2 SAN LUN Mapping Screen RS 1220 F4 5402E Shown...
Page 88: ...StorView RAID Module 80...
Page 98: ...StorView RAID Module 90...
Page 150: ...StorView RAID Module 142...
Page 184: ...StorView RAID Module 176...
Page 202: ...StorView RAID Module 194...
Page 208: ...StorView RAID Module 200...
Page 214: ...StorView RAID Module 206...