Subject: Re: [linux-audio-dev] Re: File writes with O_SYNC slow
From: Steve Lord (lord_AT_sgi.com)
Date: Thu Apr 20 2000 - 16:33:28 EEST
>
> I tried O_SYNC and even O_DSYNC on the SGI (Origin 2k),
> (D_SYNC syncs only data blocks but not metadata blocks)
> both only delivering 3.5MBytes/sec. (plain buffered writes were about
> 15-16MB/sec).
I should comment on this one since it would be on XFS....
The difference between O_SYNC and O_DSYNC on XFS is only there if the
file size does not change during the write. O_DSYNC which extends the file
still does a synchronous transaction (a bad thing) if it extents the file.
XFS tries hard to do the right things in these cases, we also have customers
who use XFS inside of things like MRI scanners, they insist that if they
write data to the disk, it better stay there, even if the power goes
out.
I realize with audio recording it is difficult to know the size of the
file in advance. But you would get better results if you bumped up
the filesize periodically rather than on every write. Preallocation
would also help.
Steve
>
> Benno.
>
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