(Illustration by Gaich Muramatsu)
> -----Original Message----- > From: Jan Harkes [mailto:jaharkes_at_cs.cmu.edu] > On Wed, May 16, 2001 at 12:38:41AM +1200, Steve Wray wrote: > > I just got into coda and now that I'm using LVM > > its going to make such experiments a lot eaiser. > > > > (this is redhat 7.1, LVM (except root and swap) > > XFS root et al). > > > > I'm using XFS as the base filesystem on /vicepa > > Is that ok? > > It doesn't matter what kind of FS is used on the server. Only the client > is picky because we need to be able to access the container files from > within the kernel to avoid bouncing all read and write calls up to > userspace. I only have 2 linux boxes, both are running RH7.1 with XFS on LVM. So, one is a client and it has XFS. I'm not sure how to interpret your comment about the client...? > > Also, I'm noticing that when I try to populate the > > /coda filesystem it seems really slow; even on the > > machine thats actually hosting that volume. [snip] > > Its like network filesystem performance, only on > > the server. > > > > What might be wrong? > > RVM is probably most of the cost. Adding and removing directory > entries (i.e. creating and deleting files) involve a lot of RVM > operations. RVM is dealt with syncronously, i.e. all modifications are > explicitly flushed and committed to disk before we return from an > operation. Also, all RVM transactions are serialized, killing any form > of gain that might come from having multiple concurrent threads. So this is an unavoidable performance problem with Coda in general? > This is aggrevated by the fact that (last time I looked) Linux tends to > write every dirty buffer to the disk when fsync is called, as there is > no record of which dirty buffers actually belong to the file we're > currently fsync'ing. Does this mean that Linux is particularly bad for Coda? Is this fixable with any tweaking? Different filesystems? > Peter Braam once measured that, given the existing server semantics and > kernel support, we could not do better than 100 RVM transactions per > second. This results in about 100 operations per second when fully > connected. > > Reintegration is far more efficient, it wraps up to 100 operations into > one big RVM transaction, so theoretically we would be able to do 10000 > operations per second in write-disconnected mode. In reality there is > just too much overhead in other areas to even get close to this kind of > performance. > > Jan > >Received on 2001-05-15 20:07:44