Configuration of swap space

I am about to 'upgrade' from RH 7.1 to RH9 by doing a fresh install. I plan to expand my swap space to accomodate my current ram, which is 1.5 Gb. Originally I had 500 Mb of ram with 1 Gb of swap, but the vendor I bought the machine from decided to make two swap partitions of 500 Mb each. Or at least that is what I have now. Following RedHat's recommendation, I plan to allow for 2 Gb of swap space. Is there any reason to split this into smaller swap partitions, or should I just make one large swap partition?

Don't. If you are more than 100MB into swap, you are in trouble. The more memory you have, the less swap you need too. So stick at 1GB and begrudge them that!

Do as you like. There is no particular advantage either way, but two is more flexible.

I agree with the above. If the OP had 500Mb of RAM and did not need more swap space, changing to 1500Mb of RAM certainly isn't going to cause a _greater_ need for swap!

If multiple partitions are set to have the same priority, they will be accessed each in turn. If they are on separate drives which can be accessed at the same time, that is exactly what will happen and the speed of swap access will be significantly increased. It works exactly the same was as the speed increase with a RAID array.

If the OP has multiple SCSI drives he can benefit from using multiple swap partitions.

... wow, i'd like to talk to the 'vendor' - that swap seems excessive. the GROT is RAM*2 to 256, then match. so if you have 512RAM, then a 512 swap partition is sufficient (and may be overkill at that). i have 256RAM machines with 128swaps running with no issues.

You are saying that if you have 32Mb of RAM you should have 64Mb of swap? I've got an old laptop with only 48Mb of RAM, and I assure you that 96Mb of RAM would result in an occasional crash!

The less RAM, the *more* swap, not the other way around.

I prefer to have at least 500Mb of virtual memory, though if you don't edit image files you probably don't need more than 200Mb. Hence, except for accidentally generating excessively huge image files, you are probably quite safe with 384Mb of virtual memory.

If you use swap at all, 100Mb is about the minimum because stale processes will be swapped out.

.... good points, well taken. hence why a GROT is GROT

I should add that I use this machine for image processing of scans of 4 x 5 negatives and I can use every bit of memory that I have. Perhaps 2 Gb is a waste, but that is what RedHat recommends, and I can afford the space, so I see no reason not to do it.

I still haven't got a clear idea on whether two swap partitions would be better than one. Peter Breuer suggested it was more flexible, but I'm not sure how.

Disk space is dirt cheap, and if there is _any_ possiblity that you might hit a peak that high, go for it.

I would note that if you are doing high resolution scans, even if the 'normal' memory usage is not that high there is still the possiblity of accidentally generating an image that is several times the size that is 'normal'; if you don't want the box to crash if that is done, more virtual memory is the way to prevent it.

If you actually use the swap space, then multiple partitions on separate drives each configured with the same priority, will be significantly faster than any of 1) a single partition, 2) multiple partitions from the same drive, or 3) any arrangment of multiple partitions each with a different priority.

I explained that in a previous article.

Thanks. That clarifies things. I must have missed the previous reference.

I think one reason RedHat recommends up to 2 Gb or swap is that it is there if you add more memory. My ASUS motherboard only has room for three slots, each of which has a 500 Mb 2100 DDR chip. Perhaps when 1 Gb chips become readily available at moderate cost, I will try to go to 3 Gb. More likely, I will have gravitated to a more powerful computer with more memory.

My experince with digital photography is that I always seem to want to do things at the limit of the technology that my budget can afford. An Imacaon which can scan 4 x 5 at 6300 ppi is way out of my range monetarily, and even if I had one, it is hard to image a system capable of handling image files that large. Also, without a LightJet printer costing $100K, I'm not sure how I would make use of such images. Of course I can always send things out to be printed, but in that case, I can probably also have the scan done that way. Typically with the large scans, it is not the scanning that taxes the system but the photoediting

> there if you add more memory. My ASUS motherboard only has room for > three slots, each of which has a 500 Mb 2100 DDR chip. Perhaps when > 1 Gb chips become readily available at moderate cost, I will try to > go to 3 Gb. More likely, I will have gravitated to a more powerful > computer with more memory. > I am starting to put together a new machine on a mother board that will hold 16GBytes of RAM. Since I get along pretty well with 512MBytes of RAM, I may well put in 4 512MByte RAM chips (so I could switch them around if I got memory problems to see which it is). I cannot imagine making a 16GByte partition for swap, even though the disk drives I am getting would easily have room.

Peter is right, of course: the more RAM you have, the less swap space you need. And RAM is so cheap that if you do more than a few pages a minute, you may wish to use more RAM rather than more swap space.

You have an odd definition of crash!

The problem is that when all is said and done, you don't know what it killed. You have no choice but to reboot.