Specifications

8 MDR User Guide
1.9 Data Readback
MDR provides several ways to read recorded data back from the disk storage system to a
host system (or vice versa for preload in a playback application).
1.9.1 Copy to File on Host via network
Recorded data (or part of it) may be copied to one or several files on the host via the
MDR network connection (Ethernet). The read back rate via Fast Ethernet is typically
less than 1 MB/s.
1.9.2 Copy to File on Host via Fibre Channel
For the fastest possible read back of the data from the disk storage system, the RAID or
JBOD disk storage system may be attached directly to the host, as shown in Chapter 5:
Host Direct Connection MDR. This requires that the host is equipped with a Fibre
Channel adapter (VMFC-2x00x-xx), and normally gives a read back speed of 40-80
MB/s, depending on the host system. In this case, the MDR board itself does not need to
be present.
1.9.3 Simultaneous Recording and Host Read/Write of disks
Read or write of disk data by the host normally takes place “offline”, after a recording is
completed. However, MDR also supports low-bandwidth host read or write traffic con-
currently with recording. Since simultaneous host access will affect the “smooth” opera-
tion of the swinging buffer DMA controllers, this is associated with a certain perform-
ance degradation. For example, 500 KB/s host traffic may result in approx. 20% reduc-
tion in maximum recording speed.
1.9.4 Disk Array Physically Moved to a Different Host
The RAID or JBOD disk storage system may also be attached to a different host
(equipped with a VMFC-2x00x-xx Fibre Channel adapter) than the one used during re-
cording, i.e. the host and disk storage system is totally de-coupled from the MDR board
itself. This can for example be used to physically move the disk array to a lab after the
recording is done in a deployed system in the field. In a playback application, this can
for example be used to preload data on the disk array before it is physically moved to the
site where real-time playback will take place through the MDR board.
1.9.5 Read to Host Memory using the API
The MDR API provides a function for reading parts of a recording to a user memory
buffer on the host system. This allows for post-processing of the recorded data by the
host without first having to store data to a file.
1.9.6 SCSI Tape Station
For backup purposes, the recorded data may be transferred from the disk storage system
onto DLT or AIT-1/2 tapes using a SCSI tape station attached to the optional SCSI con-
troller. The transfer to tape is controlled by the MDR Shell/API.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com