NFS and /dev/mdXpY

NFS and /dev/mdXpY

[Vlad Glagolev]

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Well, hello there,

I faced this problem today while trying to mount some NFS share on OpenBSD box.
I mounted it successfully without any visible errors, but I wasn't able to cd there, the printed error was:

ksh: cd: /storage - Stale NFS file handle

Apropos, the partition is 5.5 TB. I tried another one on my box and it was mounted successfully. It was possible to manage files there too. Its size is ~3GB.
That's why the first time I thought about some size limitations of OpenBSD/Linux/NFS.

While talking on #openbsd @ freenode, I discovered this via tcpdump on both sides:

http://pastebin.ca/1864713

Googling for 3 hours didn't help at all, some posts had similiar issue but either with no answer at all or without any full description.

Then I started to experiment with another Linux box to kill the possible different variants.

On another box I also have nfs-utils 1.1.6 and kernel 2.6.32. Mounting that big partition was unsuccessful, it got just stuck. On tcpdump I've seen this:

--
    172.17.2.5.884 > 172.17.2.2.2049: Flags [.], cksum 0x25e4 (correct), seq 1, ack 1, win 92, options [nop,nop,TS val 1808029984 ecr 1618999], length 0
    172.17.2.5.3565791363 > 172.17.2.2.2049: 40 null
    172.17.2.2.2049 > 172.17.2.5.884: Flags [.], cksum 0x25e6 (correct), seq 1, ack 45, win 46, options [nop,nop,TS val 1618999 ecr 1808029984], length 0
    172.17.2.2.2049 > 172.17.2.5.3565791363: reply ok 24 null
    172.17.2.5.884 > 172.17.2.2.2049: Flags [.], cksum 0x259b (correct), seq 45, ack 29, win 92, options [nop,nop,TS val 1808029985 ecr 1618999], length 0
    172.17.2.5.3582568579 > 172.17.2.2.2049: 40 null
    172.17.2.2.2049 > 172.17.2.5.3582568579: reply ok 24 null
    172.17.2.5.3599345795 > 172.17.2.2.2049: 92 fsinfo fh Unknown/0100030005030100000800000000000000000000000000000000000000000000
    172.17.2.2.2049 > 172.17.2.5.3599345795: reply ok 32 fsinfo ERROR: Stale NFS file handle POST:
    172.17.2.5.3616123011 > 172.17.2.2.2049: 92 fsinfo fh Unknown/0100030005030100000800000000000000000000000000000000000000000000
    172.17.2.2.2049 > 172.17.2.5.3616123011: reply ok 32 fsinfo ERROR: Stale NFS file handle POST:
    172.17.2.5.884 > 172.17.2.2.2049: Flags [F.], cksum 0x2449 (correct), seq 281, ack 129, win 92, options [nop,nop,TS val 1808029986 ecr 1618999], length 0
    172.17.2.2.2049 > 172.17.2.5.884: Flags [F.], cksum 0x2476 (correct), seq 129, ack 282, win 46, options [nop,nop,TS val 1618999 ecr 1808029986], length 0
    172.17.2.5.884 > 172.17.2.2.2049: Flags [.], cksum 0x2448 (correct), seq 282, ack 130, win 92, options [nop,nop,TS val 1808029986 ecr 1618999], length 0
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familiar messages, eh?

Since that time I've solved that's not OpenBSD problem. So only NFS and Linux left as the reasons of this.
It was possible to mount that small partition on Linux box too, the same as on OpenBSD.

But afterthat I recongnized an interesting issue: I have different sw raid setups on my storage server.
I tried to mount a small partition on the same md device where 5.5TB partition is located, and got the same
error message! Now I'm sure it's about NFS <-> MDADM setup, that's why I called the topic like this.

A bit about my setup:

# cat /proc/mdstat 
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4] [multipath] 
md3 : active raid1 sdc1[0] sdd1[1]
      61376 blocks [2/2] [UU]
      
md1 : active raid5 sdc2[2] sdd2[3] sdb2[1] sda2[0]
      3153408 blocks level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      
md2 : active raid5 sdc3[2] sdd3[3] sdb3[1] sda3[0]
      5857199616 blocks level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      
md0 : active raid1 sdb1[1] sda1[0]
      61376 blocks [2/2] [UU]
      
unused devices: <none>

md0, md1, and md3 aren't so interesting, since fs is created directly on them, and that's a _problem device_:

# parted /dev/md2
GNU Parted 2.2
Using /dev/md2
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p free                                                           
p free
Model: Unknown (unknown)
Disk /dev/md2: 5998GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system     Name   Flags
        17.4kB  1049kB  1031kB  Free Space
 1      1049kB  2147MB  2146MB  linux-swap(v1)  swap
 2      2147MB  23.6GB  21.5GB  xfs             home
 3      23.6GB  24.7GB  1074MB  xfs             temp
 4      24.7GB  35.4GB  10.7GB  xfs             user
 5      35.4GB  51.5GB  16.1GB  xfs             var
 6      51.5GB  5998GB  5946GB  xfs             vault
        5998GB  5998GB  507kB   Free Space

# ls /dev/md?*
/dev/md0  /dev/md1  /dev/md2  /dev/md2p1  /dev/md2p2  /dev/md2p3  /dev/md2p4  /dev/md2p5  /dev/md2p6  /dev/md3

It's very handy partitioning scheme where I can extend (grow 5th raid) with more hdds only /vault partition while "loosing" (a.k.a. not using for this partition) only ~1gb of space from every 2TB drive.

System boots ok and xfs_check passes with no problems, etc.
The only problem: it's not possible to use NFS shares on any partition of /dev/md2 device.

Finally, my question to NFS and MDADM developers: any idea?

-- 
Dont wait to die to find paradise...
--
Cheerz,
Vlad "Stealth" Glagolev

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