I've always created the file systems /boot & /root then /swap. /boot may not be necessary but I it helps me keep track of where I can find things when I'm changing grub or lilo. Even with M$ I create the C: for the system and D: for applications and data. Keeping in mind that the pagefile needs plenty of space on C: and or D:. If I'm running a 2 disk system where should the swap space be hda or hdb, and would running a separate disk for the swap space be the best way to improve performance in a server type system? Sam. On Sun, 2004-03-28 at 02:01, Ken Fuchs wrote: > Please read this: > > What follows (my reasoning - not Callum's) is not much more that "hand > waving" arguments for various rules of thumb for swap partition > allocation. The best way to evaluate swap partition location is by > duplicating actual production loads on various swap/filesystem partition > maps and seeing experimentally which is best for a particular mix of > applications. > > Ken Fuchs wrote: > > >> You could start with 256MB swap space and add swap partitions as needed. > >> However, keep in mind that modern hard drives have about twice the > >> performance on the outer cylinders than the inner cylinders, so try to > >> position swap space near the beginning of the drive for better swapping > >> performance. Swap should also be close to often used filesystems. Best > >> yet, is put swap on its own drive. > > Callum Lerwick wrote: > > >Not really a good idea for the vast majority of systems these days, > >which tend have plenty of RAM for the load upon them and thus swap > >rarely. Think about it, once you're swapping, you've already lost the > >game of performance, so why waste the speedy outer cylinders on swap? > >Its going to be better for overall system performance to use the outer > >cylinders for your filesystem, and use the slow inner cylinders for > >swap. > > I respectfully disagree with the suggestion to locate swap space at the > end of a drive. Swap space is generally a small percentage of total > disk space when using 9GB or larger drives (4GB drives are the smallest > I would use on almost any system). 512MB of swap space is large enough > for the vast majority of systems. Placing swap at the beginning > (BEGIN-SWAP) of a 9GB drive versus the end (END-SWAP) of it means about > twice as much swap performance. > > +--+--------------------------------------------------+ > BEGIN-SWAP |SS| PARTITIONED FILESYSTEM SPACE | > +--+--------------------------------------------------+ > > +--------------------------------------------------+--+ > END-SWAP | PARTITIONED FILESYSTEM SPACE |SS| > +--------------------------------------------------+--+ > > In both BEGIN-SWAP and END-SWAP, the performance of the central 8.0 GB > of the 9GB drive can be considered a constant and the performance of the > remaining 512MB of filesystem is the differentiating factor. This 512MB > of filesystem space at the beginning of END-SWAP is of course twice that > of the 512MB of filesystem space at the end of BEGIN-SWAP. Thus, using > END-SWAP as the comparison standard (performance factor = 1), the > relative filesystem performance of the PARTITIONED FILESYSTEM SPACE of > BEGIN-SWAP is 8 GB * 1 + 0.5 GB * 0.5 / 8.5 GB = 0.97. > > Thus, the BEGIN-SWAP positioning provides 512MB of swap space that is 2 > times as fast as END-SWAP and BEGIN-SWAP positioning provides 8.5 GB of > filesystem space that is 0.97 times as fast as END-SWAP. > > My conclusion: If swap is not ever going to be used, don't allocate any > swap partitions. If swap is allocated as in the BEGIN-SWAP drive map, > the swap's 2x performance versus END-SWAP will delay disk trashing due > to swapping. Note that it makes sense to put the most often used > filesystems near the beginning of the drive (since the outer cylinders > perform better than the inner). Now, for a second reason, swap at the > beginning of the drive is better because the actuator moves across fewer > cylinders between the swap partition and the highly used filesystem > partitions near the beginning of the drive. > > The above analysis assumes that if swap is needed its performance is > more critical to overall system performance than any filesystem. If > this is not the case, then clearly Callum's suggestion of placing swap > at the end of the drive has merit (assuming swap performance is less > important than the performance of all filesystems). > > However, for best swap and filesystem performance, given only one drive > to use, it may be best to place a small swap partition between every > filesystem partition. This allows the kernel to select a swap partition > on swap out based on "actuator position" and perhaps other factors. > > Without doubt, a much better location for swap is a high performance > drive dedicated exclusively for swap (which was already suggested above). > Thus, swap and filesystems would have their own dedicated disk. There > are of course more complicated multiple disk arrangements such as RAID > that provide even better performance, but they are not generally used on > single user workstation. Even, a simple, dual drive system with both > swap and filesystem partitions on both drives can be easily arranged to > outperform one disk dedicated to swap and another dedicated to > filesystems. > > >On the typical 512mb+ RAM desktop systems these days, even with as > >bloaty as GNOME/KDE can be, you're not going to be swapping enough to > >warrant wasting your outer cylinders on swap. > > That may be true, depending on application load. However, the more RAM > a system has the less swap it needs. Even a 512MB swap at the beginning > of a 9GB drive degrades filesystem performance on the rest of the drive > by only 3%. If 512MB is too big, use 256MB (2% filesystem degradation) > or 128MB (1% filesystem degradation) swap at the beginning of the drive > or make smaller swap partition throughout the entire drive. If there is > so much RAM that swap would never be used don't allocate swap space at > all or reallocate swap space for filesystem use. > > Filesystem degradation is 3% due to placing 512MB swap at the beginning > of a 9GB drive versus placing swap at the end. This seems to be a small > price to pay for swap that is twice as fast. Even if that 2x speed swap > is not needed, the penalty is only 3%. This penalty will not even > affect system performance unless the system is already close to being > I/O bound. Most often, desktop systems are "user" bound (waiting for > user mouse and keyboard input). In any case, the warm fuzzy feeling of > having 2x swap in case one needs it, probably out weights the 3% > penalty hit to filesystem performance for the vast majority of users. > > >If your system really is swapping hard enough to warrant putting swap on > >the outer cylinders, meaning a vast majority of your disk IO bandwidth > >on a given disk is dominated by swapping traffic, you really ought to be > >buying more RAM anyway. Its so cheap after all! <note: some sarcasm> > > Yes, if your disk(s) are trashing, you need more RAM or a higher > performing arrangement of swap and filesystem partitions. Remember > that Disk I/O bandwidth due to swapping will be reduced by half by using > the outer disk cylinders versus the inner disk cylinders, assuming that > the outer cylinders perform twice as fast as the inner cylinders which > is very often true (or close to the truth depending on the actual disk > drive used). > > ------ > > Finally, since swap space is a part of the virtual memory system it > would be generally best to use the fastest partition on a disk drive to > help emulate memory. There should be a good reason to not use the > fastest partition on a disk drive such as distributing swap space > throughout the entire disk when all filesystems are utilized about the > same amount and the actuator could be anywhere at any given moment > rather than near the often used swap and filesystems at the beginning of > the drive. > > Alternatively, if actuator position becomes a dominant factor, swap (or > some of it) in the middle of the drive may be better than all swap at > the beginning or end. > > Anyone who has read this far into this message deserves an award of some > sort and may have enough energy left to search for research on this > subject and report it to the list. Perhaps, we might all learn > something more in the process and be subjected to fewer ramblings such > as the one I've just written above. > > Sincerely, > > Ken Fuchs <kfuchs at winternet.com> > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > http://www.mn-linux.org tclug-list at mn-linux.org > https://mailman.real-time.com/mailman/listinfo/tclug-list _______________________________________________ TCLUG Mailing List - Minneapolis/St. Paul, Minnesota http://www.mn-linux.org tclug-list at mn-linux.org https://mailman.real-time.com/mailman/listinfo/tclug-list