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Old 08-15-2008, 07:23 PM
"Stephen Carville"
 
Default read and write size in NFS v4

I am migrating my NFS file server from RHEL3 to RHEL5 and moving up to
NFS v4 where i can. Once question I still have is what is the maximum
rsize and wsize i can set for V4 automount? The file
include/linux/nfsd/const.h says teh maximum is 32*1024 (32K) but some
google postings claim that does not apply to V4; I've tried v4
automounts with values up to 1048576 and none of the machine have
complained.

A part of the new server's duties will be to accept the RMAN (oracle)
backups so speed is important. I am using a dedicated gigabit switch
with jumbo frames (9000 bytes) and I have tuned the TCP for the
"private" interfaces on all the connected interfaces. These is the
only parameter I am not sure what I can get away with. I have it set
to 32768 for the current v3 setup.

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Stephen Carville

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Old 08-16-2008, 08:14 PM
Yong Huang
 
Default read and write size in NFS v4

> From: "Stephen Carville" <stephen.carville@gmail.com>
> Subject: read and write size in NFS v4
> To: "General Red Hat Linux discussion list" <redhat-list@redhat.com>
>
> I am migrating my NFS file server from RHEL3 to RHEL5 and moving up to
> NFS v4 where i can. Once question I still have is what is the maximum
> rsize and wsize i can set for V4 automount? The file
> include/linux/nfsd/const.h says teh maximum is 32*1024 (32K) but some
> google postings claim that does not apply to V4; I've tried v4
> automounts with values up to 1048576 and none of the machine have
> complained.
>
> A part of the new server's duties will be to accept the RMAN (oracle)
> backups so speed is important. I am using a dedicated gigabit switch
> with jumbo frames (9000 bytes) and I have tuned the TCP for the
> "private" interfaces on all the connected interfaces. These is the
> only parameter I am not sure what I can get away with. I have it set
> to 32768 for the current v3 setup.
>
> --
> Stephen Carville

I don't know the answer. But can you check nfsstat to see what it says the size
is? Also, strace some read and write operations and see what the return values
for read() and write() are. But I guess the latter method may not tell us the
underlined driver level chunk size.

Yong Huang




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Old 08-19-2008, 03:04 PM
"Stephen Carville"
 
Default read and write size in NFS v4

On Sat, Aug 16, 2008 at 1:14 PM, Yong Huang <yong321@yahoo.com> wrote:
>> From: "Stephen Carville" <stephen.carville@gmail.com>
>> Subject: read and write size in NFS v4
>> To: "General Red Hat Linux discussion list" <redhat-list@redhat.com>
>>
>> I am migrating my NFS file server from RHEL3 to RHEL5 and moving up to
>> NFS v4 where i can. Once question I still have is what is the maximum
>> rsize and wsize i can set for V4 automount? The file
>> include/linux/nfsd/const.h says teh maximum is 32*1024 (32K) but some
>> google postings claim that does not apply to V4; I've tried v4
>> automounts with values up to 1048576 and none of the machine have
>> complained.
>>
>> A part of the new server's duties will be to accept the RMAN (oracle)
>> backups so speed is important. I am using a dedicated gigabit switch
>> with jumbo frames (9000 bytes) and I have tuned the TCP for the
>> "private" interfaces on all the connected interfaces. These is the
>> only parameter I am not sure what I can get away with. I have it set
>> to 32768 for the current v3 setup.
>>
>> --
>> Stephen Carville
>
> I don't know the answer. But can you check nfsstat to see what it says the size
> is? Also, strace some read and write operations and see what the return values
> for read() and write() are. But I guess the latter method may not tell us the
> underlined driver level chunk size.

Tried that but it doesn't seem to tell me what the actual block size
is. However I found that /proc/mounts does record the wsize and rsize
and a little experimentation led me to conclude that the default is
32768 and the max is 32768.

--
Stephen Carville

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