stat-ing a file makes the fs acquire a readlock (PR) forcing the other node
to downgrade from writelock (EX) which then forces it to flush the dirty
pages
to disk. Say you have 500M to flush and your iscsi setup's io thruput is
30MB/s.
That'll be 16 secs.
Note: The nodes are not frozen. The ls and cp processes are waiting on the
pages to flush to disk.
You can confirm this by repeating the test and doing a "find ." instead
of ls.
The former will not stat the file (will only stat the directory) and
thus avoid
the force flush seen above.
Yuri Kirsanov wrote:
Good day, everyone.
I have SAN server build with Openfiler OS, with iSCSI mode turned on. I have
two nodes, which connect to that server via iSCSI, using one of two active
iSCSI partitions. I've installed ocfs2 1.3.3 with kernel 2.6.23.1, configured
it, made ocfs2 partition and was successful in mounting it on both nodes.
Everything works just fine, I can upload file from one node and delete it
using another one, except for one strange thing. When I'm using ocfs2 mounted
partition from one node, for example, uploading 1Gb test file into it, and I
try to access that partition from another node - just to read directory, for
example, - both nodes "freeze" for about 15-20 seconds, both operations just
stops for a while, and then copying continues on first node, while second one
gets directory listing.
I have no errors on both nodes, neither iSCSI ones, no ocfs2. All three
servers are joined together using 1Gbit/sec network switch and there's no
other machines on that switch.
If you need any information, please feel free to ask me about it. Thanks in
advance!
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