Hello list, I have a doubt. When creating an ext3 fs, 5% of its space is reserved to the superuser. I understand this should be important for /, maybe /var and /tmp. But is it compulsory for other fs, like, say, an external disk with data? Or it's just a heritage, no more needed? Could one safely reclaim this 5%? I understand that no other fs (jfs, xfs, reiser) reserves some space. Thanks for clarification
On Tue, Aug 28, 2007 at 03:29:46PM +0200, beevis at libero.it wrote:> Hello list, > I have a doubt. When creating an ext3 fs, 5% of its space is reserved to the superuser. > I understand this should be important for /, maybe /var and /tmp. > But is it compulsory for other fs, like, say, an external disk with data? > Or it's just a heritage, no more needed? Could one safely reclaim this 5%? > I understand that no other fs (jfs, xfs, reiser) reserves some space.You can, but the performance of the filesystem will go down as you use the last 5%, especially if the filesystem is dynamic and constantly changing, since it will cause the files to become very badly fragmented. UFS historically used 10% for its anti-fragmentation reserve. With ext3 we decreased it to 5%. If the filesystem is going to be essentially static after you fill it up, sure you can reduce it down to 0%. But if the filesystem is going to be continuously active, you will get better performance by buying a bigger hard drive and using a filesystem with an average utilization of 50-80% than one which is hovering between 99-100%. Aside from spending 100-200 Euro's on extra memory, speading 100-200 Euro's on a newer, bigger hard drive can be one of the easist and cheapest way to improve the performance of your system. Regards, - Ted
> Hello list, > I have a doubt. When creating an ext3 fs, 5% of its space is reserved to the superuser. > I understand this should be important for /, maybe /var and /tmp. > But is it compulsory for other fs, like, say, an external disk with data? > Or it's just a heritage, no more needed? Could one safely reclaim this 5%? > I understand that no other fs (jfs, xfs, reiser) reserves some space.You can, but the performance of the filesystem will go down as you use the last 5%, especially if the filesystem is dynamic and constantly changing, since it will cause the files to become very badly fragmented. UFS historically used 10% for its anti-fragmentation reserve. With ext3 we decreased it to 5%. If the filesystem is going to be essentially static after you fill it up, sure you can reduce it down to 0%. But if the filesystem is going to be continuously active, you will get better performance by buying a bigger hard drive and using a filesystem with an average utilization of 50-80% than one which is hovering between 99-100%. Aside from spending 100-200 Euro's on extra memory, speading 100-200 Euro's on a newer, bigger hard drive can be one of the easist and cheapest way to improve the performance of your system. Regards, - Ted Thanks for clarification. So I understand this 5% is reserved in order to prevent fragmentation.