(Illustration by Gaich Muramatsu)
On Wed, Jun 19, 2002 at 10:37:44AM +0200, srickaue_at_mail.eds.ch wrote: > we at EDS are evaluating CODA for our web server farm. We use SuSE Linux > 8.0 (Kernel 2.4.18) and set up one SCM and two Non-SCMs (release 5.3.19-1). > All machines are conntected with 100Mbit links. Each of the machine has > ~30GB disk space. We set up a replicated volume called "wwwroot" over all > three machines. Log and data partitions are raw devices: log is 30M and > data 1G. > > We now experience an extreme performance problem. Creating and/or copying a > file with 1MB needs aprox. 1 Minute (!). The log files doesn't show any > problems as far as I can see. Strange, here is my result on a triply replicated volume. I'm connected over a 100Mbit-HD link to the servers, which are connected to a switch and have 100Mbit-FD between them. The servers are PentiumII-200's with 128MB of memory (maybe 256MB). Just to show that I'm not write-disconnected. jaharkes_at_ravel:/coda/usr/jaharkes/test$ cfs lv . Status of volume 0x7f000492 (2130707602) named "vmm:u.jaharkes" Volume type is ReadWrite Connection State is Connected Minimum quota is 0, maximum quota is unlimited Current blocks used are 8592 The partition has 160118 blocks available out of 2350051 Write-back is disabled And here is the time it takes me to store 1MB. jaharkes_at_ravel:/coda/usr/jaharkes/test$ time dd if=/dev/zero of=testfile bs=1024 count=1024 1024+0 records in 1024+0 records out real 0m0.549s user 0m0.000s sys 0m0.010s So this is about 100 times faster than what you're seeing. Did some more timings, write-disconnected, first store (create + store) real 0m0.492s second store (store only) real 0m0.014s connected first store (create + store) real 0m0.483s second store (store only) real 0m0.430s Running it a couple of times shows that connected mode stores are all typically around 1/2 second, whether we create or overwrite the file. When disconnected, only the create takes approximately half a second, but all subsequent stores are in the order of 2/100ths of a second. Connected store-only should be faster than the create+store because we only need one RPC instead of two. Not sure why these operations are the same speed, it is probably the data transfer that is taking most of the time here. Write-disconnected create should be a lot faster, we are not sending any data or RPCs to the servers. Not sure where the time is lost here. JanReceived on 2002-06-19 09:52:52