On Wed, Feb 09, 2005 at 06:07:41AM -0800, Jeff Dinisco wrote: > > Could you explain why filesystem performance will degrade when the last > 5% is used? I have several 1TB filesystems w/ only 1% reserved. The > man page describes this space as "reserved for the super-user". I > always assumed this was a buffer for root to be able to perform > operations on a full filesystem. It seems as though 10GB is more than > enough. Is this not the case? There are two reasons for the reserve. One is to reserve space on the partition containing /var and /etc for log files, etc. The other is to avoid the performance degredation when the last 5-10% of the disk space is used. (BSD actually reserves 10% by default.) Given that the cost of a 200 GB disks is under $100 USD the cost of reserving 10GB is approximately $5.00 USD, or approximately the cost of a large cup of coffee at Starbucks. Why is does the filesystem performance degrade? Because as the last blocks of a filesystem are consumed the probability of filesystem fragmentation goes up dramatically? Exactly when this happens depends on the write patterns of the workload and the distribution of the file sizes on the filesystem, but on average this tends to happen when the utilization rises to 90-95%. - Ted _______________________________________________ Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
