Lvol residing in memory?

[Stuart Coombes]

Is anyone aware if HP-UX 11.00 LVM is able to create a filesystem and have it reside in memory rather than physical disk.

I have had a request from a colleague who is implementing an Informatica solution on HP-UX 11.00. My colleague says the following:

'...on a big file, Informatica is spilling to disk a larger amount of intermediate data. If some how I can mount a logical volume to a memory location, redirect informatica to use that logical volume I will consequently read/write to RAM instead of physical disk and improve performance.
Typically the file system would be mounted under the root volume group but
physically any files created in it will be created in memory....'

I cannot think of a way this would be done because LVM is a disk manipulation tool. However, if anyone does have any solutions which will allow a file to reside in memory with read/write capabilities I would be very interested.

Thanks

[Bill Hassell]

This is commonly referred to as a RAMDISK and while there is an undocumented ramdisk driver for HP-UX, it is designed only for use with install/recovery kernels. It has severe (and undocumented) limitations including a small size (max=64 megs I think).

The concept of RAMDISK is very old but Unix has pretty much eliminated the need with the buffer cache. Most CPU intensive math applications write very little to disk so it is questionable as to what benefit the RAMDISK might be.

In general, the buffer cache handles buffering to the disk quite well for all but very disk intensive operations (hundreds of I/Os per second). This of course assumes that you have massive amounts of RAM, say 4 to 8 Gbytes and can set your buffer cache to hundreds of megs. As with all questions about performance on any system, the answer is "it depends".

[Sandor Horvath_2]

Hi !

What do You think about Solid State Disk ???

It is very expensive but it is a RAM Disk.

regards, Saa