Thanks everyone for the great INFO... This was EXACTLY what I needed and had a very hard time finding out. The mount -t tmpfs -o size=1g none /ramdisk worked perfectly. I needed temporary ram space to use as disk space. Thanks!
Just to explain further, the "images" are not ISO's... These are hard drive images, like GHOST files (only using a Linux free application). But to further explain, even if I mounted an ISO, there would still be disk IO.. I'm trying to eliminate the disk I/O from the equation so I can be downloading 20 or 25 machines at the same time. Since the server us a dual 2.0gig Xeon and I have gig all the way from the server to the desktop.. This should scream!
Thanks again.
Scott
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Craig White Sent: Thursday, March 31, 2005 10:38 AM To: centos@centos.org Subject: Re: [CentOS] Odd Question... MAX Ram Disk Size
On Thu, 2005-03-31 at 09:59 -0600, Aleksandar Milivojevic wrote:
Scott Heisler wrote:
I want to put that image file on a RAMDISK on my server. The image file is between 3 and 4 gig. I have 6 gig in the server, so plenty of memory. I modified GRUB to increase the size of my ram
disk... First I started with a 200mb, that worked group, formatted,
etc.
Then I tried 1gig - everything looks like it works but when I mount it, it tells me the volume is not formatted or has invalid super
blocks.
Perhaps I'm exceeding the allowable built-in ramdisk limit, but I couldn't find any docs anywhere that would tell me what that limit
was.
When you say ramdisk, do you mean ramdisk as in ramsdisk device (hardware) that keeps information accross system reboots and/or power cycles, or ramdisk as in file system that exists only in your server's
RAM and is lost each time machine is rebooted? Not clear from your question. You mention having "enough RAM for it in server" (which would imply later), but you also say that you are looking for "device"
(which would imply former).
If you are looking for self-contained device, there are many solid state disks (SSD) available on the market. Basically, they look like disk, the "only" difference is instead of having magnetic plates, they
store information into internal RAM (either battery backed up, or of the non-volatile type). System sees them as normal IDE/SATA/SCSI/FC drive (depending on the interface), and you don't need to have anything special to access them. The speed is usually limited by interface used and type of memory used (obviously EEPROM based SSD will have much worse write times then DRAM with battery backup based
SSD).
If you are looking for solution to use your server's memory as temporary RAM disk (you don't care information being lost when you reboot or power cycle), something like this works nicely:
# mount -t tmpfs -o size=8g none /ramdisk
That would create 8GB memory-based file system. The memory file system uses is swappable. So just make sure free RAM + free swap is larger than 8GB, and you should be fine. Of course, you can create smaller or larger system too. Basically it is the same thing as tmpfs
on Solaris systems. I kind of like to mount /tmp this way (of course,
with much smaller size, usually 32-128MB, depending on server's
needs).
Or you can place it in fstab to have it always available:
none /ramdisk tmpfs size=8g 0 0
---- this is great info and I suppose I might find use for it someday but wouldn't a loop mount from an iso file (the disk image) be better for this purpose?
Craig
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