storage devices should be supported by reliable backup procedures to
ensure the integrity of the stored data.
This is especially true of SDRAM-based storage devices, since
SDRAM is inherently volatile.
For this reason, power should not be removed from the RAM-SAN
unless a separate copy of the data has been stored in a non-volatile
external backup. Several different options exist for
implementing such a backup, ranging from simple to sophisticated, with
the choice of a specific backup option left to the user.
simplest RAM-SAN backup solution is to have the RAM-SAN mirror all
write operations to a network RAID.
Simply adding a RAM-SAN to an existing storage area network and
configuring it for mirrored storage operation achieves this goal.
All READ operations are serviced by the RAM-SAN for maximum
performance, while all WRITE operations are performed simultaneously
by the RAM-SAN and a network RAID for maximum data persistence.
This approach offers the best of both worlds – performance
and persistence – and provides the added benefit that the RAM-SAN
can serve as a short-term backup for the RAID device.
method encouraged by most SSD suppliers is the use of a dedicated hard
disk (or RAID) to which the SSD will dump data under conditions of
impending power failure.
If such a failure is detected in one of the RAM-SAN's
hot-swappable redundant power supplies, the RAM-SAN can store the
entire contents of its memory to this device.
Devices for this purpose may be supplied by TMS or by a third
party, allowing maximum flexibility in the choice of a particular
Users may opt for a very fast and sophisticated backup method,
a relatively simple backup method, or no backup method at all.
support of these backup methods, TMS supplies a dedicated RAID
controlled by the RAM-SAN.
This RAID can be configured for mirrored storage operation or
for dedicated power-failure backup operation.
Depending upon the particular external storage device, a
full-capacity RAM-SAN (128 Gbytes) can be dumped to disk in as little
as 30 minutes.
For smaller-capacity RAM-SANs, the maximum required backup time
decreases linearly with decreasing memory capacity.