Thread: Harddisk performance degrading over time?
Do the hard disk degrade in performance over time on a Linux ext2 filesystem? All my performance test programs show 20% worse performance and I have done NADA! I just ran them again :(
Do you have to defrag?
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Daniel Åkerud
Daniel Åkerud
[ Don't underestimate the power of stupid people in large groups]
Actually, the culprit is probably PostgreSQL and not the ext2 file system. Have you tried vacuuming you database and running the benchmarks again? PostgreSQL uses a non-overwriting storage manager, and so vacuum needs to be run periodically to clear out expired tuples. Jason --- Daniel_�kerud <zilch@home.se> wrote: > Do the hard disk degrade in performance over time on > a Linux ext2 filesystem? All my performance test > programs show 20% worse performance and I have done > NADA! I just ran them again :( > > Do you have to defrag? > > --- > Daniel �kerud > > [ Don't underestimate the power of stupid people in > large groups] > __________________________________________________ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/
Oh yeah, vacuuming is not the problem here. Thanks anyway... :) And also, it seems that it is the indexed searches that is suffering the most. The non-indexed searches is less affected. This is not only PostgreSQL but also MySQL. The database is totally restored each test run. Daniel Åkerud > > Actually, the culprit is probably PostgreSQL and not > the ext2 file system. Have you tried vacuuming you > database and running the benchmarks again? PostgreSQL > uses a non-overwriting storage manager, and so vacuum > needs to be run periodically to clear out expired > tuples. > > Jason > > --- Daniel_Åkerud <zilch@home.se> wrote: > > Do the hard disk degrade in performance over time on > > a Linux ext2 filesystem? All my performance test > > programs show 20% worse performance and I have done > > NADA! I just ran them again :( > > > > Do you have to defrag? > > > > --- > > Daniel Åkerud > > > > [ Don't underestimate the power of stupid people in > > large groups] > > > > > __________________________________________________ > Do You Yahoo!? > Get personalized email addresses from Yahoo! Mail > http://personal.mail.yahoo.com/ >
> Oh yeah, > vacuuming is not the problem here. > > Thanks anyway... :) > > And also, it seems that it is the indexed searches that is suffering the > most. The non-indexed searches is less affected. This is not only PostgreSQL > but also MySQL. I know the BSD filesystems are self-defragmenting. I don't know if the ext2 filesystems are the same. Surely someone must know. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
On Sun, 24 Jun 2001, Bruce Momjian wrote: > > Oh yeah, > > vacuuming is not the problem here. > > > > Thanks anyway... :) > > > > And also, it seems that it is the indexed searches that is suffering the > > most. The non-indexed searches is less affected. This is not only PostgreSQL > > but also MySQL. > > I know the BSD filesystems are self-defragmenting. I don't know if the > ext2 filesystems are the same. Surely someone must know. Not exactly, BSD ffs (fast filesystem) isn't self-defragmenting, it just fragments differently [less than] ext2 :) See this for paper and some tools to get ffs fragmentation stats: http://www.eecs.harvard.edu/~margo/usenix.195 (it has links to critique of the paper as well) There's a tool ftp://ftp.uk.linux.org/pub/linux/sct/defrag/ to defrag ext2 filesystem, but its considered to be alpha quality and not really maintained.
> On Sun, 24 Jun 2001, Bruce Momjian wrote: > > > > Oh yeah, > > > vacuuming is not the problem here. > > > > > > Thanks anyway... :) > > > > > > And also, it seems that it is the indexed searches that is suffering the > > > most. The non-indexed searches is less affected. This is not only PostgreSQL > > > but also MySQL. > > > > I know the BSD filesystems are self-defragmenting. I don't know if the > > ext2 filesystems are the same. Surely someone must know. > Not exactly, BSD ffs (fast filesystem) isn't self-defragmenting, it just > fragments differently [less than] ext2 :) Yes, BSD is more "doesn't fragment much" rather than "self defragmenting". > See this for paper and some tools to get ffs fragmentation stats: > http://www.eecs.harvard.edu/~margo/usenix.195 > (it has links to critique of the paper as well) > > There's a tool ftp://ftp.uk.linux.org/pub/linux/sct/defrag/ to defrag ext2 > filesystem, but its considered to be alpha quality and not really > maintained. Yes, thanks for the clarification. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
ext2 doesn't need to be defrag'ed either. You CAN, but it shouldn't need it unless you are doing something very strange. Ole Gjerde ----- Original Message ----- From: "Bruce Momjian" <pgman@candle.pha.pa.us> To: "Daniel Åkerud" <zilch@home.se> Cc: "Jason Earl" <jdearl@yahoo.com>; "PostgreSQL-general" <pgsql-general@postgresql.org> Sent: Sunday, June 24, 2001 10:57 PM Subject: Re: Harddisk performance degrading over time? > > Oh yeah, > > vacuuming is not the problem here. > > > > Thanks anyway... :) > > > > And also, it seems that it is the indexed searches that is suffering the > > most. The non-indexed searches is less affected. This is not only PostgreSQL > > but also MySQL. > > I know the BSD filesystems are self-defragmenting. I don't know if the > ext2 filesystems are the same. Surely someone must know.
OK, so now I know it wasn't that. The strange thing is just that, that looking at all the test values collected, it seems like only indexed inserts and indexed selects has gotten slower for BOTH PostgreSQL and MySQL, Never mind... as long as it is maximally slow now ;) *kidding* Daniel Åkerud > ext2 doesn't need to be defrag'ed either. You CAN, but it shouldn't need it > unless you are doing something very strange. > > Ole Gjerde > > ----- Original Message ----- > From: "Bruce Momjian" <pgman@candle.pha.pa.us> > To: "Daniel Åkerud" <zilch@home.se> > Cc: "Jason Earl" <jdearl@yahoo.com>; "PostgreSQL-general" > <pgsql-general@postgresql.org> > Sent: Sunday, June 24, 2001 10:57 PM > Subject: Re: Harddisk performance degrading over time? > > > > > Oh yeah, > > > vacuuming is not the problem here. > > > > > > Thanks anyway... :) > > > > > > And also, it seems that it is the indexed searches that is suffering the > > > most. The non-indexed searches is less affected. This is not only > PostgreSQL > > > but also MySQL. > > > > I know the BSD filesystems are self-defragmenting. I don't know if the > > ext2 filesystems are the same. Surely someone must know. > > > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org >