Hello,
I finally managed to get realtime subvolumes working in my system. I
built a new kernel using the sources at SGI (Kernel 2.4.25). I have also been
testing the realtime subvolumes with my application.
The application writes data to a XFS realtime subvolume at 80
MBytes/sec. I'm using 3ware Raid Controller 7810, configured as RAID 0 with 64K
stripes.
The man page of mk.xfs says, "the real-time extent size should be
carefully chosen to match the parameters of the physical media used" - can
someone say more about this? What more do I need to know about the ophysical
media?
Here's the output generated by xfs_info:
/******************************************************/
kram@dop93:~> xfs_info /data
meta-data=/data isize=256 agcount=25, agsize=1048576 blks
= sectsz=512
data = bsize=4096 blocks=25601577, imaxpct=25
= sunit=0 swidth=0 blks, unwritten=0
naming =version 2 bsize=4096
log =internal bsize=4096 blocks=12500, version=1
= sectsz=512 sunit=0 blks
realtime =external extsz=65536 blocks=208836967,
rtextents=13052310
/****************************************************/
The RAID controller document says that smaller stripe width is more
suited for sequential access, and that is what I do. I use preallocated files
in realtime subvolume. What I see is the disk-pack exhibits some sort of
sponginess with time. Is it entirely due to the RAID Controller + harddisk
combination, or is it something from XFS realtime subvolumes? I can include some
statistics of the latencies if you need.
Thank you.
Regards
Ramesh
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