Memory Requirements
ESS memory usage can range from
moderate to staggering, depending on
the size of the array, the "memory
model" in use, and the mode that ESS
is operating in. In most cases,
memory usage, although signifigant,
should not pose a barrier to using
ESS.
Linear Mode
In linear mode, there are two ESS
options that impact memory usage.
Standard Linear Mode
In this mode, the amount of
memory needed depends on the
physical size of the array and the
logical size of the available
addressing space.
For arrays < 4 TB in size,
multiply the logical size by 0.1%.
Thus a 2TB array with 1.8TB
available will need 1.8GB of RAM.
For arrays > 4TB in size,
multiple the logical size by 0.125%.
Thus an 8 TB array with 7.2TB
available will need 9GB of RAM.
Linear Mode with Error Detection
In this mode, a non cryptographic
hash is maintained along with each
4K block. This allows the driver to
"verify" that every block written is
"correct".
For arrays < 1PB in size,
multiply the logical size by 0.2%.
Thus a 16 TB array with 14.4TB
available will need 28.8GB of RAM.
Compressed Mode
Compressed Mode works very
similarly to Linear Mode with an
option for Error Detection. With
compressed mode, it is likely that
the Logical size will actually be
larger than the physical size.
Standard Compressed Mode
For arrays < 256 GB in size,
multiply the logical size by 0.125%.
Thus a 200GB array with 180GB
available will need 225 MB of RAM.
For arrays < 64 TB in size,
multiply the logical size by 0.150%.
Thus a 20TB array with 30TB
available will need 45 GB of RAM.
For arrays < 16 PB in size,
multiple the logical size by 0.175%.
Thus a 100TB array with 200TB
available will need 350 GB of RAM.
Compressed Mode with Error
Detection
For arrays < 64 TB in size,
multiply the logical size by 0.2%.
For arrays < 16 PB in size,
multiple the logical size by 0.225%.
Deduplication Mode
Deduplication mode, by itself, is
not currently supported.
Deduplication and Compressed Mode
can be used with the compression
level set to "none" to emulate this.
Deduplication and Compression
Mode
Dedupe and Compressed (DDC) mode
can have very high memory usage
value, especially for large arrays
with large "data reduction" factors.
For this reason, several
memory modes are available to
mitigate memory issues.
Further documentation on DDC
memory usage is in work. Contact
support@easyco.com if you wish to
discuss particular configuration.