10 messages in org.freebsd.freebsd-performanceDisk I/O Performance| From | Sent On | Attachments |
|---|---|---|
| Kristofer Pettijohn | Oct 19, 2004 12:34 pm | |
| João Carlos Mendes Luís | Oct 19, 2004 12:45 pm | |
| Mike Horwath | Oct 19, 2004 1:52 pm | |
| Kristofer Pettijohn | Oct 19, 2004 2:01 pm | |
| Kristofer Pettijohn | Oct 19, 2004 2:02 pm | |
| Mike Horwath | Oct 19, 2004 2:02 pm | |
| Mike Horwath | Oct 19, 2004 2:04 pm | |
| Kristofer Pettijohn | Oct 19, 2004 2:06 pm | |
| Mike Jakubik | Oct 19, 2004 2:08 pm | |
| João Carlos Mendes Luís | Oct 20, 2004 8:33 am |
| Subject: | Disk I/O Performance | |
|---|---|---|
| From: | João Carlos Mendes Luís (jon...@jonny.eng.br) | |
| Date: | Oct 20, 2004 8:33:00 am | |
| List: | org.freebsd.freebsd-performance | |
Mike Horwath wrote:
On Tue, Oct 19, 2004 at 04:45:03PM -0300, Jo?o_Carlos_Mendes_Lu?s wrote:
I'd say that you have to check which CCD chunk size is best for your needs. The manual for vinum recommends avoiding chunk sized to a power of two, which is probably the first big mistake of everybody.
Try mounting with option noatime, if you haven't already. And use the largest block size possible when formatting. Last time I read about there was a limit of 16384, but I would expect better performance for large file with 64k blocks (and 8k frags).
If you don't have a need for safety on the files, you could try mount async and measure if it suits better you need for performance than softupdates. Sometimes softupdates is faster, and it is always safer.
All good ideas except the issue is bandwidth performance across the disks.
I am seeing the same thing (and Kristofer and I have been working together, kinda, on this). It is as if I/O is being preferred for writing vs reading, very weird.
His 5 disk stripe (well, it used to be five when I managed the machine) should not have issues, but this recently begun happening both on his systems and some of mine.
Did you make a software upgrade recently? This could point to some changes in the device driver. If this is the case, them a downgrade could help.
Indeed, I would expect that, if both happened at the same time, write should have more preference than read. This would release buffers faster and keep sensible data in RAM for the minimum time possible. Of course, only after softupdates have released the data for writing, at the block device level.