Memory based disks or Solid state disks (SSD) are based on
the concept of RAM disks. However, they are relatively more stable. An SSD is
very similar to a standard disk drive and, for most practical purposes, behaves
like one. To the host system, an SSD is a disk drive. But an SSD does not store
data on magnetic disk media. Instead, it stores data on high density arrays of
high speed DRAM memory chips. This eliminates the inherent mechanical delays
that come with the need to spin a hard disk and position the read/write heads
to execute an I/O request. By eliminating such latencies, SSDs achieve access
times much faster than conventional disk drives.
With most vendors, SSD performance is fast and reliable. An
SSD has an integral battery-powered hard-disk drive and associated software continuously
backing up its contents. At any moment, typically 81 percent of the data on the
SSD is backed up to the hard disk. During power failures, batteries maintain
power long enough to back up the rest of the data. In some implementations,
backing up the contents onto disk is handled at the hardware level, enhancing
performance and reliability further.
For database applications, SSDs provide a viable option for
enhancing performance by eliminating variable seek times without compromising
availability. Most vendors implement custom versions of the SSD concept. An
instance, Sun Microsystems has PrestoServe, a high speed static memory-based
storage medium that is backed up by lithium powered batteries. In typical
Oracle implementations, small but heavy accessed files, such as online redo
logs, Undo data files, can be placed on SSDs.
Most implementations of SSDs incorporate highly resilient
fault monitoring during regular operations, which includes continuous header
checking and data-retention system monitoring. However, have a chat with your
vendor’s technical personnel and ensure that such checks are indeed continuous
in your case. Also, have an arrangement with your vendor so that their
technical personnel can visit your site and perform data-integrity checks at
regular intervals, at least every three or four months. If possible, purchase tools
from the vendor to conduct such tests in house, more often if necessary. For more assistance about performance tuning, kindly check our remote dba support services or directly contact us.
