[Ocfs2-users] OCFS2 strage freezes
Sunil Mushran
Sunil.Mushran at oracle.com
Tue Mar 4 10:50:39 PST 2008
No delay in read as we won't have to flush those pages to disk.
Yuri Kirsanov wrote:
> Yes, now I see it, thank you very much. So, it happends only when a
> large amount of data has to be flushed to disk on target system, right?
>
> Then, if I already have big file and just reading it from server,
> there will be no delays in access from two nodes, right?
>
> ----- Original Message ----- From: "Sunil Mushran"
> <Sunil.Mushran at oracle.com>
> To: "Yuri Kirsanov" <flash at preferance.ru>
> Cc: <ocfs2-users at oss.oracle.com>
> Sent: Tuesday, March 04, 2008 9:28 PM
> Subject: Re: [Ocfs2-users] OCFS2 strage freezes
>
>
>> 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!
>>>
>>> _______________________________________________
>>> Ocfs2-users mailing list
>>> Ocfs2-users at oss.oracle.com
>>> http://oss.oracle.com/mailman/listinfo/ocfs2-users
>>>
>>
>>
>
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