[Ocfs2-users] OCFS2 strage freezes

[Sunil Mushran]

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
>>>
>>
>>
>