On 3/28/11 1:27 PM, Oren Elrad wrote: > On Mon, Mar 28, 2011 at 2:06 PM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote: >> On 3/28/11 1:02 PM, Oren Elrad wrote: >>> Undesired behavior; mke2fs defaults to reserving 5% of the volume for >>> the root user. 5% of a 2TB volume is 100GB. The rationale for root >>> reservation (syslogd, etc...) does not require 100GB. As volumes get >>> larger, this default makes less and less sense. >>> >>> Proposal; If the user does not specify their preferred reserve_ratio >>> on the command-line (-m), use the less of 5% or MAX_RSRV_SIZE. I >>> propose 10GiB as a sensible maximum default reservation for root. >>> >>> Patch: Follows and http://capsid.brandeis.edu/~elrad/e2fsprog.gitdiff >>> >>> Tested on the latest git+patch, RHEL5 (2.6.18-194.17.1.el5) with a >>> 12TB volume (which would reserve 600GB under the default!): >> >> There's been a bit of debate about this; is the space really saved >> for root, or is it to stop the allocator from going off the rails >> when the fs nears capacity? Both, really. >> >> I don't really have a horse in the race, but the complaint has certainly >> come up before... it's just important to realize that the space isn't >> only there for root's eventual use. >> >> No other fs that I know of enforces this "don't fill the fs to capacity" >> common sense programatically, though. >> >> -Eric >> > > [SNIP] > > Well, in my version you still get some reservation to prevent whatever > woes (fragmentation, allocator slow-down) that accompany a nearly-full > disk. If you think 25 or 50GiB is a more appropriate maximum default, > I have no objections. the question is, how much is enough? (isn't that always the question?) :) What constitutes "nearly full?" > Whatever the reason for reservation, more than 100GB is totally > nonsensical IMHO. That depends; 1% sounds small, until the total is a Petabyte. For overall performance, it may well be the % that matters, not the absolute number. It really could probably use more real investigation, and less hand-waving (of which I am also guilty). :) -Eric > Oren Elrad > Dept. of Physics > Brandeis University -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
