RamDisk on HP-UX 11

[Chairote Thitipatarakor_2]

Is it possible to setup Ram Disk on HP-UX 11.
If so, please suggest.

Regards,

[Randy Mather]

do you mean swap space ?
if so, yes you can setup device swap, or virtual memory

[Terence Wong_1]

check out the web site http://www.soliddata.com

[John Scheller]

AppMate Performance Software sells a product called RamDisc that works on HP-UX 11.x

http://www.ramdisc.com/ramdsk.html

Regards,
John

[John Scheller]

The RamDisc product from AppMate Performance Software is supported on hpux 11.x

http://www.ramdisc.com/ramdsk.html

Regards,
John

[John Scheller]

The RamDisc product from AppMate Performance Software is supported on hpux 11.23

http://www.ramdisc.com/ramdsk.html

Regards,
John

[Laurent Menase]

Hi there is no supported ramdisk


else on 11iV[23]:
#lsdev |grep ramdisc
9 9 ramdisc pseudo
# mknod /dev/rramdisc c 9 0x10000

# mknod /dev/ramdisc b 9 0x10000
# newfs -F hfs /dev/rramdisc
# mkdir /tmp/ram
# mount /dev/ramdisc /tmp/ram

the last parameter is the size of the ramdisc is the size.
WARNING that parameter is really limited.
And once a ramdisc allocation is failed only reboot

on 11i
the ramdisc is really limited to small sizes, and have some side effects in regards of real disc.
Indeed the latency is low, but access to ramdisc cause cpu copy - and not DMA copy like when it is on a real disk.

[NMory]

Ram disks are unsupported by HP.

But check this old link:

http://www.faqs.org/faqs/hp/hpux-faq/section-81.html

[Marco A.]

Yes, HP-UX 9.00 and later include a RAM disk driver. The driver is NOT officially supported by HP for customer use. Comments in the header file "/usr/conf/sio/ram.h" describe how to add RAM disk support to the kernel, as well as how to create a RAM disk.

Here are several reasons why using RAM disks is RISKY business:

1. As stated above, RAM disks are unsupported by HP.
2. It is unclear (to me anyway) how "locking" down memory interacts with normal memory management, including pageouts and memory pseudo-swap.

The comments in /usr/conf/sio/ram.h says say:

"Depending on the availability of memory, allocating large amounts of memory for RAM disk volumes may cause system failures (panics or hangs)."

3. RAM disks can waste memory space.

The "usable" yield of disk space from memory allocated may be less than 100%. (1 GB of real memory may yield less than 1 GB on "disk space".)

4. RAM disks aren't saved over a reboot, and require special action to do so.

5. You must write a C program to delete them from a running system.


Here are the basic steps make a 128 MB RAM disk on HP-UX 10.x/11.x:

1. Modify your kernel to include the RAM disk driver:

# cd /stand/build
# /usr/lbin/sysadm/system_prep -v -s system
# kmsystem -c y -S system ram
# mk_kernel -s system
# mv ../system ../system.prev
# cp ../vmunix ../vmunix.prev
# mv system ..
# mv vmunix_test ../vmunix
# cd /
# shutdown -r

Note: "ramdisc" is an alias for "ram" that is also recognized.

2. Set up the device files and mount the RAM disk filesystem:

# mknod /dev/rram1 c 9 0x008001
# mknod /dev/ram1 b 9 0x008001
# newfs -F hfs /dev/rram1
# mkdir -p /ramdisk
# mount /dev/ram1 /ramdisk

Another way
===========

There is a better, but not free, way to _simulate_ a RAM disk under HP-UX 10.20 or later...

You must first purchase and install the optional OnlineJFS product, the advanced bundle for the VxFS file system. This enables a number of extra mount options for VxFS filesystems.


To configure a VxFS filesystem so that most buffer cache flushes are prevented, specify the following options when mounting the filesystem:

"tmplog,mincache=tmpcache,convosync=delay"

The first two options can be configured with sam, but the convosync option must be edited into /etc/fstab by hand.

A description and pricing info for the OnlineJFS product is available at <> (just search for "onlinejfs").

A third way
===========

JTL Technical Services, LLC, sells a software product for HP-UX called RamDisc. There are two versions - RamDisc plus and RamDisc classic. For more information see their web site:

o <>

I hope this helps,

Best regards,

Marco