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post #3 of (permalink) Old 04-11-2013, 05:44 AM - Thread Starter
Brokenstorm
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Summary and conclusion


Let's me start by saying that there s no perfect RAMDisks. Each has its strengths and flaws and whether those are relevant to you is highly dependent on how you decide to make use of the RAMDisk.
That being said, I'll try to objectively list the pros and cons of each software.


ArchiCrypt Ramdisk
Pros:
-Paid version offers encryption

Cons:
-Only available in German
-Slowest RAMDisk tested
-Slow response time
-IO/s don't scale with high queue depth
-Runs as a service (Save on shutdown might be interrupted by WaitToKillServiceTimeout)


Bond Disc
Pros:
-Free
-Excellent performance
-Has a lot of archival and encryption options
-Only writes the changes made to an image

Cons:
-Maximum size of 640MB
-Can only use a FAT filesystem
-Image Load/Save is relatively slow
-Unintuitive interface
-Development has stopped


Buffalo Ramdisk
Pros:
-Free

Cons:
-2nd slowest RAMDisk tested
-Can only use a FAT32 filesystem
-Require reboot to change RAMDisk size
-Hides the memory it uses from the OS
-IO/s don't scale with queue depth
-Can't change the backup location


Dataram RAMDisk
Pros:
-Good performance

Cons:
-Rewrites the whole image, even when no changes have been made
-Setting changes only apply after the RAMDisk has been unmounted


Gilisoft RAMDisk
Pros:
-Excellent performance

Cons:
-Extremely slow response time on random read/write
-IO/s don't scale with queue depth
-Can have problems creating very large image files
-I had problems creating a RAMDisk after removing one


Gizmo Drive
Pros:
-Free
-Good performance

Cons:
-No backup options
-Maximum size of 4GB
-Can only use a NTFS filesystem


ImDisk
Pros:
-Free
-Open source
-Good performance

Cons:
-Only manual backups


Passmark OSFMount
Pros:
-Free
-Good performance

Cons:
-Only manual backups


Primo Ramdisk Ultimate
Pros:
-Excellent performance
-Offers both SCSI and Direct-IO
-Only writes the changes made to an image
-Offers the most options of all the programs tested

Cons:
-Initial image takes a long time to create


RamPhantomEX
Pros:
-Good performance

Cons:
-Only available in Japanese


SoftPerfect RAM Disk
Pros:
-Free
-Excellent performance

Cons:
-Performance decreases on large RAMDisks
-IO/s don't scale with high queue depth
-Rewrites the whole image, even when no changes have been made


StarWind RAM Disk
Pros:
-Free
-Good performance

Cons:
-No backup options


SuperSpeed RamDisk Plus
Pros:
-Excellent performance

Cons:
-Rewrites the whole image, even when no changes have been made


VSuite Ramdisk Server
Pros:
-Excellent performance
-Good set of features

Cons:
-Slow creation speed for large RAMDisks
-Primo RAMDisk can do everything it does better and is cheaper


WinRamTech (QSoft)
Pros:
-Best performance of all the RAMDisk tested
-Only writes the changes made to an image

Cons:
-Initial image takes a long time to create
-Extremely difficult to manage more than 1 image, especially if they are of different sizes




Other considerations

FAT32 vs NTFS
FAT32
Pros:
-Faster
Cons:
-4GB maximum file size

NTFS
Pros:
-No file size limit
Cons:
-Doesn’t scale well with high queue depth


SCSI vs Direct-IO
SCSI
Pros:
-Recognized by Windows Disk Management and almost all disk management utilities
-Can be used as a RAW drive by a Virtual Machine
Cons:
-Slower than Direct-IO

Direct-IO
Pros:
-Better performance than a SCSI disk (especially on accessing small files)
Cons:
-Treated as a logical disk (not visible to some disk management utilities)


Cluster size
Cluster size may have an impact on performance.
Cluster size smaller than 4k will hurt performance (since DRAM has a 4k cluster size)
Cluster size bigger than 4k may increase performance but will also increase wasted space


Bottlenecks
CPU: In most cases memory bandwidth will be limited by the speed of the CPU. There is no easy way to tell how much bandwidth the processor can handle, the only way to know for sure is to test it with a benchmark. That is because even with identical clocks this value will vary based on the processor architecture and memory controller, but as a general rule of thumb higher frequency result in more memory bandwidth.

RAM: Unlike with CPUs, it's very easy to determine the maximum memory bandwidth of DDR2/3. Simply multiply the memory frequency by 8 (since DDR2/3 transfers data on a 64bits wide bus) to get the peak transfer rate in MB/s. For single threaded application this will be your peak bandwidth. To determine the peak bandwidth for multi-threaded application you need to multiply the peak transfer rate by the number of memory channels your CPU supports (either 2, 3 or 4).

Now compare that value with the one you got for your CPU. If they are very close then your memory is likely limiting your memory bandwidth, otherwise your CPU is the bottleneck. This is useful information to have when trying to determine which product to buy to optimize your memory bandwidth. It can also help to get a better understanding of why Anvil's, ATTO and CrystalDiskMark report different results in certain cases.

ATTO and CrystalDiskMark use a single thread to determine a drive performance. So for example, with 1600MHz DDR3 those tool will never report speeds higher than 12.5GB/s for a RAMDisk. On the other hand, Anvil's use 4 thread for tests with a queue depth of 4 and 16 for those with a queue depth of 16 and therefore could report higher speed in those tests.

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