HP StorageWorks Storage Mirroring Recover User's Guide (T5437-96008, November 2009)

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not perform as well as a mirrored or non-parity striped set because writing to
a RAID 5 array incurs the overhead of generating and writing parity data.
RAID 5 write performance can be up to 50% less than the write performance
of a single disk, depending on the adapter and disk.
Another option is to use a solid state disk, which are hard drives that use
RAM instead of disk platters. These devices are typically quite costly, but
they will provide superior performance as a queuing device when the best
performance is required.
Note:
Scanning the Storage Mirroring Recover queue files for viruses can
cause unexpected results. If anti-virus software detects a virus in a
queue file and deletes or moves it, data integrity on the target cannot
be guaranteed. As long as you have your anti-virus software
configured to protect the actual production data, the anti-virus
software can clean, delete, or move an infected file and the clean,
delete, or move will be replicated to the target. This will keep the
target from becoming infected and will not impact the Storage
Mirroring Recover queues.
● Maximum system memory for queue—This is the amount of Windows
system memory, in MB, that will be used to store data in queues. When
exceeded, queuing to disk will be triggered. This value is dependent on the
amount of physical memory available but has a minimum of 32 MB. By
default, 128 MB or 512 MB of memory is used, depending on your operating
system. If you set it lower, Storage Mirroring Recover will use less system
memory, but you will queue to disk sooner which may impact system
performance. If you set it higher, Storage Mirroring Recover will maximize
system performance by not queuing to disk as soon, but the system may
have to swap the memory to disk if the system memory is not available.
Since the source is typically running a production application, it is important
that the amount of memory Storage Mirroring Recover and the other
applications use does not exceed the amount of RAM in the system. If the
applications are configured to use more memory than there is RAM, the
system will begin to swap pages of memory to disk and the system
performance will degrade. For example, by default an application may be
configured to use all of the available system memory when needed, and this
may happen during high-load operations. These high-load operations cause
Storage Mirroring Recover to need memory to queue the data being changed
by the application. In this case, you would need to configure the applications
so that they collectively do not exceed the amount of RAM on the server.
Perhaps on a server with 1 GB of RAM running the application and Storage