Re: clustered MD

2015-06-22 Thread NeilBrown
On Sun, 14 Jun 2015 17:19:31 -0500 Goldwyn Rodrigues wrote: > > > On 06/12/2015 01:46 PM, David Teigland wrote: > > When a node fails, its dirty areas get special treatment from other nodes > > using the area_resyncing() function. Should the suspend_list be created > > before any reads or

Re: clustered MD

2015-06-22 Thread NeilBrown
On Sun, 14 Jun 2015 17:19:31 -0500 Goldwyn Rodrigues rgold...@suse.com wrote: On 06/12/2015 01:46 PM, David Teigland wrote: When a node fails, its dirty areas get special treatment from other nodes using the area_resyncing() function. Should the suspend_list be created before any

Re: clustered MD

2015-06-14 Thread Goldwyn Rodrigues
On 06/12/2015 01:46 PM, David Teigland wrote: When a node fails, its dirty areas get special treatment from other nodes using the area_resyncing() function. Should the suspend_list be created before any reads or writes from the file system are processed by md? It seems to me that gfs journal

Re: clustered MD

2015-06-14 Thread Goldwyn Rodrigues
On 06/12/2015 01:46 PM, David Teigland wrote: When a node fails, its dirty areas get special treatment from other nodes using the area_resyncing() function. Should the suspend_list be created before any reads or writes from the file system are processed by md? It seems to me that gfs journal

Re: clustered MD

2015-06-12 Thread David Teigland
When a node fails, its dirty areas get special treatment from other nodes using the area_resyncing() function. Should the suspend_list be created before any reads or writes from the file system are processed by md? It seems to me that gfs journal recovery could read/write to dirty regions (from

Re: clustered MD

2015-06-12 Thread David Teigland
When a node fails, its dirty areas get special treatment from other nodes using the area_resyncing() function. Should the suspend_list be created before any reads or writes from the file system are processed by md? It seems to me that gfs journal recovery could read/write to dirty regions (from

Re: clustered MD

2015-06-10 Thread Neil Brown
On Wed, 10 Jun 2015 16:07:44 -0500 David Teigland wrote: > On Thu, Jun 11, 2015 at 06:31:31AM +1000, Neil Brown wrote: > > What is your interest in this? I'm always happy for open discussion and > > varied input, but it would help to know to what extent you are a stake > > holder? > > Using

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 04:07:44PM -0500, David Teigland wrote: > > Also a slightly less adversarial tone would make me feel more > > comfortable, though maybe I'm misreading your intent. > > You're probably misreading "concerned". > > The initial responses to my inquiry were severely lacking in

Re: clustered MD

2015-06-10 Thread David Teigland
On Thu, Jun 11, 2015 at 06:31:31AM +1000, Neil Brown wrote: > What is your interest in this? I'm always happy for open discussion and > varied input, but it would help to know to what extent you are a stake > holder? Using the dlm correctly is non-trivial and should be reviewed. If the dlm is

Re: clustered MD

2015-06-10 Thread Neil Brown
On Wed, 10 Jun 2015 10:01:51 -0500 David Teigland wrote: > Isn't this process what staging is for? No it isn't. Staging is useful for code drops. i.e. multiple other developers want to collaborate to improve some code that the maintainer doesn't want to accept. So it goes into staging, "the

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 12:05:33PM -0500, David Teigland wrote: > Separate bitmaps for each node sounds like a much better design than the > cmirror design which used a single shared bitmap (I argued for using a > single bitmap when cmirror was being designed.) Sorry misspoke, I argued for one

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 11:23:25AM -0500, Goldwyn Rodrigues wrote: > To start with, the goal of (basic) MD RAID1 is to keep the two > mirrored device consistent _all_ of the time. In case of a device > failure, it should degrade the array pointing to the failed device, > so it can be

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
To start with, the goal of (basic) MD RAID1 is to keep the two mirrored device consistent _all_ of the time. In case of a device failure, it should degrade the array pointing to the failed device, so it can be (hot)removed/replaced. Now, take the same concepts to multiple nodes using the same

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
On 06/10/2015 10:01 AM, David Teigland wrote: On Tue, Jun 09, 2015 at 10:33:08PM -0500, Goldwyn Rodrigues wrote: some real world utility to warrant the potential maintenance effort. We do have a valid real world utility. It is to provide high-availability of RAID1 storage over the cluster.

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 10:27:27AM -0500, Goldwyn Rodrigues wrote: > I thought I answered that: > To use a software RAID1 across multiple nodes of a cluster. Let me > explain in more words.. > > In a cluster with multiple nodes with a shared storage, such as a > SAN. The shared device becomes a

Re: clustered MD

2015-06-10 Thread David Teigland
On Tue, Jun 09, 2015 at 10:33:08PM -0500, Goldwyn Rodrigues wrote: > >>>some real world utility to warrant the potential maintenance effort. > >> > >>We do have a valid real world utility. It is to provide > >>high-availability of RAID1 storage over the cluster. The > >>distributed locking is

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
On 06/10/2015 03:00 AM, Richard Weinberger wrote: On Wed, Jun 10, 2015 at 5:33 AM, Goldwyn Rodrigues wrote: David Lang has already responded: The idea is to use a RAID device (currently only level 1 mirroring is supported) with multiple nodes of the cluster. Here is a description on how to

Re: clustered MD

2015-06-10 Thread Richard Weinberger
On Wed, Jun 10, 2015 at 5:33 AM, Goldwyn Rodrigues wrote: > David Lang has already responded: The idea is to use a RAID device > (currently only level 1 mirroring is supported) with multiple nodes of the > cluster. > > Here is a description on how to use it: >

Re: clustered MD

2015-06-10 Thread Richard Weinberger
On Wed, Jun 10, 2015 at 5:33 AM, Goldwyn Rodrigues rgold...@suse.com wrote: David Lang has already responded: The idea is to use a RAID device (currently only level 1 mirroring is supported) with multiple nodes of the cluster. Here is a description on how to use it:

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
On 06/10/2015 03:00 AM, Richard Weinberger wrote: On Wed, Jun 10, 2015 at 5:33 AM, Goldwyn Rodrigues rgold...@suse.com wrote: David Lang has already responded: The idea is to use a RAID device (currently only level 1 mirroring is supported) with multiple nodes of the cluster. Here is a

Re: clustered MD

2015-06-10 Thread David Teigland
On Tue, Jun 09, 2015 at 10:33:08PM -0500, Goldwyn Rodrigues wrote: some real world utility to warrant the potential maintenance effort. We do have a valid real world utility. It is to provide high-availability of RAID1 storage over the cluster. The distributed locking is required only

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
To start with, the goal of (basic) MD RAID1 is to keep the two mirrored device consistent _all_ of the time. In case of a device failure, it should degrade the array pointing to the failed device, so it can be (hot)removed/replaced. Now, take the same concepts to multiple nodes using the same

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 10:27:27AM -0500, Goldwyn Rodrigues wrote: I thought I answered that: To use a software RAID1 across multiple nodes of a cluster. Let me explain in more words.. In a cluster with multiple nodes with a shared storage, such as a SAN. The shared device becomes a single

Re: clustered MD

2015-06-10 Thread Goldwyn Rodrigues
On 06/10/2015 10:01 AM, David Teigland wrote: On Tue, Jun 09, 2015 at 10:33:08PM -0500, Goldwyn Rodrigues wrote: some real world utility to warrant the potential maintenance effort. We do have a valid real world utility. It is to provide high-availability of RAID1 storage over the cluster.

Re: clustered MD

2015-06-10 Thread Neil Brown
On Wed, 10 Jun 2015 10:01:51 -0500 David Teigland teigl...@redhat.com wrote: Isn't this process what staging is for? No it isn't. Staging is useful for code drops. i.e. multiple other developers want to collaborate to improve some code that the maintainer doesn't want to accept. So it goes

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 12:05:33PM -0500, David Teigland wrote: Separate bitmaps for each node sounds like a much better design than the cmirror design which used a single shared bitmap (I argued for using a single bitmap when cmirror was being designed.) Sorry misspoke, I argued for one

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 11:23:25AM -0500, Goldwyn Rodrigues wrote: To start with, the goal of (basic) MD RAID1 is to keep the two mirrored device consistent _all_ of the time. In case of a device failure, it should degrade the array pointing to the failed device, so it can be

Re: clustered MD

2015-06-10 Thread David Teigland
On Thu, Jun 11, 2015 at 06:31:31AM +1000, Neil Brown wrote: What is your interest in this? I'm always happy for open discussion and varied input, but it would help to know to what extent you are a stake holder? Using the dlm correctly is non-trivial and should be reviewed. If the dlm is

Re: clustered MD

2015-06-10 Thread Neil Brown
On Wed, 10 Jun 2015 16:07:44 -0500 David Teigland teigl...@redhat.com wrote: On Thu, Jun 11, 2015 at 06:31:31AM +1000, Neil Brown wrote: What is your interest in this? I'm always happy for open discussion and varied input, but it would help to know to what extent you are a stake holder?

Re: clustered MD

2015-06-10 Thread David Teigland
On Wed, Jun 10, 2015 at 04:07:44PM -0500, David Teigland wrote: Also a slightly less adversarial tone would make me feel more comfortable, though maybe I'm misreading your intent. You're probably misreading concerned. The initial responses to my inquiry were severely lacking in any

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? It first appeared in December, 2014 on the RAID mailing list. http://marc.info/?l=linux-raid=141891941330336=2 I

Re: clustered MD

2015-06-09 Thread David Lang
On Tue, 9 Jun 2015, David Teigland wrote: We do have a valid real world utility. It is to provide high-availability of RAID1 storage over the cluster. The distributed locking is required only during cases of error and superblock updates and is not required during normal operations, which makes

Re: clustered MD

2015-06-09 Thread David Teigland
;>I've just noticed the existence of clustered MD for the first time. > >>>It is a major new user of the dlm, and I have some doubts about it. > >>>When did this appear on the mailing list for review? > >> > >>It first appeared in December, 2014 on the RAID mailing

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
Hi David, On 06/09/2015 02:45 PM, David Teigland wrote: On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
Hi David, On 06/09/2015 02:45 PM, David Teigland wrote: On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some

Re: clustered MD

2015-06-09 Thread David Teigland
On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: > On 06/09/2015 01:22 PM, David Teigland wrote: > >I've just noticed the existence of clustered MD for the first time. > >It is a major new user of the dlm, and I have some doubts about it. > >When did this

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? It first appeared in December, 2014 on the RAID mailing

clustered MD

2015-06-09 Thread David Teigland
I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of

clustered MD

2015-06-09 Thread David Teigland
I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? Dave -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? It first appeared in December, 2014 on the RAID mailing

Re: clustered MD

2015-06-09 Thread David Lang
On Tue, 9 Jun 2015, David Teigland wrote: We do have a valid real world utility. It is to provide high-availability of RAID1 storage over the cluster. The distributed locking is required only during cases of error and superblock updates and is not required during normal operations, which makes

Re: clustered MD

2015-06-09 Thread David Teigland
On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list

Re: clustered MD

2015-06-09 Thread David Teigland
On Tue, Jun 09, 2015 at 03:08:11PM -0500, Goldwyn Rodrigues wrote: Hi David, On 06/09/2015 02:45 PM, David Teigland wrote: On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
Hi David, On 06/09/2015 02:45 PM, David Teigland wrote: On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
Hi David, On 06/09/2015 02:45 PM, David Teigland wrote: On Tue, Jun 09, 2015 at 02:26:25PM -0500, Goldwyn Rodrigues wrote: On 06/09/2015 01:22 PM, David Teigland wrote: I've just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some

Re: clustered MD

2015-06-09 Thread Goldwyn Rodrigues
just noticed the existence of clustered MD for the first time. It is a major new user of the dlm, and I have some doubts about it. When did this appear on the mailing list for review? It first appeared in December, 2014 on the RAID mailing list. http://marc.info/?l=linux-raidm=141891941330336w=2 I