Re: [lustre-discuss] lustre write wrong data under postgresql benchmark tool test(concurrent access same data file with primary node write and standy node read)

[Michael Nishimoto]

Hi Andreas,

I didn't see an answer back, but I have a followup question.  Also, my
Postgres knowledge is pretty much zero.

I understand your concern about using direct I/O and how application
buffers can cause problems.
My question is about a statement in the original email, a reference to
shutting down Postgres
on the standby node and running pg_xlogdump which I assume is a standalone
command.

Shouldn't a standalone command running on the standby node see a consistent
copy of data?

I assume that active and standby nodes are Lustre clients in the same
cluster.

Thanks,

Michael

On Sat, Sep 29, 2018 at 2:54 PM Andreas Dilger 
wrote:

> Is PG using O_DIRECT or buffered read/write?  Is it caching the pages in
> userspace?
>
> Lustre will definitely keep pages consistent between clients, but if the
> application is caching the pages in userspace, and does not have any
> protocol between the nodes to invalidate cached pages when they are
> modified on disk, then the data will become inconsistent when one node
> modifies it.
>
> That is the same reason it isn't possible to mount a single ext4
> filesystem r/w on one node and r/o on another node with shared storage,
> because the filesystem doesn't expect data to be changing underneath it,
> and will cache pages in RAM and not re-read them if they are modified on
> the other node.
>
> Cheers, Andreas
>
> On Sep 29, 2018, at 07:57, 王亮  wrote:
>
> Hello, lustre development team
>
>
> background: we have two postgresql instances running as a primary and
> standby and they share the same xlog file and data files (we change PG code
> to achieve this) which located in the mounted lustre file system, and we
> want to have a try with the lustre file system, we used gfs2 before, and we
> expect the lustre will show a much better performance, but ...
>
>
>
> We meet a read/write concurrent access problem related with Lustre. Would
> you like to give us some suggestions? Any advices are appreciated, and
> thank you in advanced : )
>
> note: we are very sure the standy instance will not write any data to
> disk. (to be sure of this, we also shutdown the standby end, and use
> pg_xlogdump tool to read the xlog file, the problem still happened, and
> pg_xlogdump to is just a query to with any write operation)
>
>
>
> Scenario Description:
>
> There’re 4 nodes(CentOS Linux release 7.4) connected with infiniband
> network(driven by MLNX_OFED_LINUX-4.4):
>
> 10.0.0.106 acts as MDS with a local PCI-E 800GB SSD that used as MDT.
>
> 10.0.0.101 acts as OSS with a same local PCI-E 800GB SSD that used as OST.
>
> 10.0.0.104 and 10.0.0.105 act as Lustre client and mount the Lustre file
> system at the directory of “/lustre”.
>
> The Lustre related packages are compiled from official
> lustre-2.10.5-1.src.rpm.
>
>
>
> The simplest verification(i.e. dd command) passed without errors.
>
>
>
> Error:
>
> Then start our customized PostgreSQL service at 104 and 105. 104 runs as
> the primary PostgreSQL server, and 105 runs as the secondary PostgreSQL
> server. All the two PostgreSQL nodes read/write the shared directory of “
> /lustre” provided by Lustre. The primary PostgreSQL server will open
> files with **RW** mode and write something into the files; at the *
> *meantime** the second PostgreSQL server will open the same files with *
> *R** mode and read the data written by the primary PostgreSQL server, and
> it gets the **wrong** data (the flushed data by primary in disk is error
> i.e. write wrong data into disk). This will happen when we run a benchmark
> tool of PostgreSQL.
>
>
>
>
>
> PS 1.
>
> We tried different options to mount the Lustre:
>
> mount -t lustre -o flock 10.0.0.106@o2ib0:/birdfs /lustre
>
> mount -t lustre -o flock -o ro 10.0.0.106@o2ib0:/birdfs /lustre
>
> but the error always exists.
>
>
>
> PS 2.
>
> Attach the initial information, maybe helpful.
>
> [root@106 ~]# mkfs.lustre --fsname=birdfs --mgs --mdt --index=0
> --reformat /dev/nvme0n1
>
>
>
>Permanent disk data:
>
> Target: birdfs:MDT
>
> Index:  0
>
> Lustre FS:  birdfs
>
> Mount type: ldiskfs
>
> Flags:  0x65
>
>   (MDT MGS first_time update )
>
> Persistent mount opts: user_xattr,errors=remount-ro
>
> Parameters:
>
>
>
> device size = 763097MB
>
> formatting backing filesystem ldiskfs on /dev/nvme0n1
>
>target name   birdfs:MDT
>
>4k blocks 195353046
>
>options-J size=4096 -I 1024 -i 2560 -q -O
> dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E
> lazy_journal_init -F
>
> mkfs_cmd = mke2fs -j -b 4096 -L birdfs:MDT  -J size=4096 -I 1024 -i
> 2560 -q -O dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E
> lazy_journal_init -F /dev/nvme0n1 195353046
>
>
>
> Writing CONFIGS/mountdata
>
>
>
> [root@101 ~]# mkfs.lustre --fsname=birdfs --ost --reformat --index=0
> --mgsnode=10.0.0.106@o2ib0 /dev/nvme0n1
>
>
>
>Permanent disk data:
>
> Target: birdfs:OST
>
> Index:  0
>
> Lustre FS:  birdfs
>

Re: [lustre-discuss] lustre write wrong data under postgresql benchmark tool test(concurrent access same data file with primary node write and standy node read)

[Andreas Dilger]

Is PG using O_DIRECT or buffered read/write?  Is it caching the pages in 
userspace?

Lustre will definitely keep pages consistent between clients, but if the 
application is caching the pages in userspace, and does not have any protocol 
between the nodes to invalidate cached pages when they are modified on disk, 
then the data will become inconsistent when one node modifies it.

That is the same reason it isn't possible to mount a single ext4 filesystem r/w 
on one node and r/o on another node with shared storage, because the filesystem 
doesn't expect data to be changing underneath it, and will cache pages in RAM 
and not re-read them if they are modified on the other node.

Cheers, Andreas

On Sep 29, 2018, at 07:57, 王亮 
mailto:wanzifore...@gmail.com>> wrote:

Hello, lustre development team

background: we have two postgresql instances running as a primary and standby 
and they share the same xlog file and data files (we change PG code to achieve 
this) which located in the mounted lustre file system, and we want to have a 
try with the lustre file system, we used gfs2 before, and we expect the lustre 
will show a much better performance, but ...

We meet a read/write concurrent access problem related with Lustre. Would you 
like to give us some suggestions? Any advices are appreciated, and thank you in 
advanced : )
note: we are very sure the standy instance will not write any data to disk. (to 
be sure of this, we also shutdown the standby end, and use pg_xlogdump tool to 
read the xlog file, the problem still happened, and pg_xlogdump to is just a 
query to with any write operation)


Scenario Description:
There’re 4 nodes(CentOS Linux release 7.4) connected with infiniband 
network(driven by MLNX_OFED_LINUX-4.4):
10.0.0.106 acts as MDS with a local PCI-E 800GB SSD that used as MDT.
10.0.0.101 acts as OSS with a same local PCI-E 800GB SSD that used as OST.
10.0.0.104 and 10.0.0.105 act as Lustre client and mount the Lustre file system 
at the directory of “/lustre”.
The Lustre related packages are compiled from official lustre-2.10.5-1.src.rpm.

The simplest verification(i.e. dd command) passed without errors.

Error:
Then start our customized PostgreSQL service at 104 and 105. 104 runs as the 
primary PostgreSQL server, and 105 runs as the secondary PostgreSQL server. All 
the two PostgreSQL nodes read/write the shared directory of “/lustre” provided 
by Lustre. The primary PostgreSQL server will open files with *RW* mode and 
write something into the files; at the *meantime* the second PostgreSQL server 
will open the same files with *R* mode and read the data written by the primary 
PostgreSQL server, and it gets the *wrong* data (the flushed data by primary in 
disk is error i.e. write wrong data into disk). This will happen when we run a 
benchmark tool of PostgreSQL.


PS 1.
We tried different options to mount the Lustre:
mount -t lustre -o flock 
10.0.0.106@o2ib0:/birdfs /lustre
mount -t lustre -o flock -o ro 
10.0.0.106@o2ib0:/birdfs /lustre
but the error always exists.

PS 2.
Attach the initial information, maybe helpful.
[root@106 ~]# mkfs.lustre --fsname=birdfs --mgs --mdt --index=0 --reformat 
/dev/nvme0n1

   Permanent disk data:
Target: birdfs:MDT
Index:  0
Lustre FS:  birdfs
Mount type: ldiskfs
Flags:  0x65
  (MDT MGS first_time update )
Persistent mount opts: user_xattr,errors=remount-ro
Parameters:

device size = 763097MB
formatting backing filesystem ldiskfs on /dev/nvme0n1
   target name   birdfs:MDT
   4k blocks 195353046
   options-J size=4096 -I 1024 -i 2560 -q -O 
dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E 
lazy_journal_init -F
mkfs_cmd = mke2fs -j -b 4096 -L birdfs:MDT  -J size=4096 -I 1024 -i 2560 -q 
-O dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E 
lazy_journal_init -F /dev/nvme0n1 195353046

Writing CONFIGS/mountdata

[root@101 ~]# mkfs.lustre --fsname=birdfs --ost --reformat --index=0 
--mgsnode=10.0.0.106@o2ib0 /dev/nvme0n1

   Permanent disk data:
Target: birdfs:OST
Index:  0
Lustre FS:  birdfs
Mount type: ldiskfs
Flags:  0x62
  (OST first_time update )
Persistent mount opts: ,errors=remount-ro
Parameters: mgsnode=10.0.0.106@o2ib

device size = 763097MB
formatting backing filesystem ldiskfs on /dev/nvme0n1
   target name   birdfs:OST
   4k blocks 195353046
   options-J size=400 -I 512 -i 69905 -q -O 
extents,uninit_bg,dir_nlink,quota,huge_file,flex_bg -G 256 -E 
resize="4290772992",lazy_journal_init -F
mkfs_cmd = mke2fs -j -b 4096 -L birdfs:OST  -J size=400 -I 512 -i 69905 -q 
-O extents,uninit_bg,dir_nlink,quota,huge_file,flex_bg -G 256 -E 
resize="4290772992",lazy_journal_init -F /dev/nvme0n1 195353046
Writing CONFIGS/mountdata


Looking forward to any replies.

Regards,
Bird

[lustre-discuss] lustre write wrong data under postgresql benchmark tool test(concurrent access same data file with primary node write and standy node read)

[王亮]

Hello, lustre development team


background: we have two postgresql instances running as a primary and
standby and they share the same xlog file and data files (we change PG code
to achieve this) which located in the mounted lustre file system, and we
want to have a try with the lustre file system, we used gfs2 before, and we
expect the lustre will show a much better performance, but ...



We meet a read/write concurrent access problem related with Lustre. Would
you like to give us some suggestions? Any advices are appreciated, and
thank you in advanced : )

note: we are very sure the standy instance will not write any data to disk.
(to be sure of this, we also shutdown the standby end, and use pg_xlogdump
tool to read the xlog file, the problem still happened, and pg_xlogdump to
is just a query to with any write operation)



Scenario Description:

There’re 4 nodes(CentOS Linux release 7.4) connected with infiniband
network(driven by MLNX_OFED_LINUX-4.4):

10.0.0.106 acts as MDS with a local PCI-E 800GB SSD that used as MDT.

10.0.0.101 acts as OSS with a same local PCI-E 800GB SSD that used as OST.

10.0.0.104 and 10.0.0.105 act as Lustre client and mount the Lustre file
system at the directory of “/lustre”.

The Lustre related packages are compiled from official
lustre-2.10.5-1.src.rpm.



The simplest verification(i.e. dd command) passed without errors.



Error:

Then start our customized PostgreSQL service at 104 and 105. 104 runs as
the primary PostgreSQL server, and 105 runs as the secondary PostgreSQL
server. All the two PostgreSQL nodes read/write the shared directory of “
/lustre” provided by Lustre. The primary PostgreSQL server will open files
with **RW** mode and write something into the files; at the **meantime**
the second PostgreSQL server will open the same files with **R** mode and
read the data written by the primary PostgreSQL server, and it gets the *
*wrong** data (the flushed data by primary in disk is error i.e. write
wrong data into disk). This will happen when we run a benchmark tool of
PostgreSQL.





PS 1.

We tried different options to mount the Lustre:

mount -t lustre -o flock 10.0.0.106@o2ib0:/birdfs /lustre

mount -t lustre -o flock -o ro 10.0.0.106@o2ib0:/birdfs /lustre

but the error always exists.



PS 2.

Attach the initial information, maybe helpful.

[root@106 ~]# mkfs.lustre --fsname=birdfs --mgs --mdt --index=0 --reformat
/dev/nvme0n1



   Permanent disk data:

Target: birdfs:MDT

Index:  0

Lustre FS:  birdfs

Mount type: ldiskfs

Flags:  0x65

  (MDT MGS first_time update )

Persistent mount opts: user_xattr,errors=remount-ro

Parameters:



device size = 763097MB

formatting backing filesystem ldiskfs on /dev/nvme0n1

   target name   birdfs:MDT

   4k blocks 195353046

   options-J size=4096 -I 1024 -i 2560 -q -O
dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E
lazy_journal_init -F

mkfs_cmd = mke2fs -j -b 4096 -L birdfs:MDT  -J size=4096 -I 1024 -i
2560 -q -O dirdata,uninit_bg,^extents,dir_nlink,quota,huge_file,flex_bg -E
lazy_journal_init -F /dev/nvme0n1 195353046



Writing CONFIGS/mountdata



[root@101 ~]# mkfs.lustre --fsname=birdfs --ost --reformat --index=0
--mgsnode=10.0.0.106@o2ib0 /dev/nvme0n1



   Permanent disk data:

Target: birdfs:OST

Index:  0

Lustre FS:  birdfs

Mount type: ldiskfs

Flags:  0x62

  (OST first_time update )

Persistent mount opts: ,errors=remount-ro

Parameters: mgsnode=10.0.0.106@o2ib



device size = 763097MB

formatting backing filesystem ldiskfs on /dev/nvme0n1

   target name   birdfs:OST

   4k blocks 195353046

   options-J size=400 -I 512 -i 69905 -q -O
extents,uninit_bg,dir_nlink,quota,huge_file,flex_bg -G 256 -E
resize="4290772992",lazy_journal_init -F

mkfs_cmd = mke2fs -j -b 4096 -L birdfs:OST  -J size=400 -I 512 -i 69905
-q -O extents,uninit_bg,dir_nlink,quota,huge_file,flex_bg -G 256 -E
resize="4290772992",lazy_journal_init -F /dev/nvme0n1 195353046

Writing CONFIGS/mountdata





Looking forward to any replies.



Regards,

Bird


-- 
regards
denny
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