Re: [zfs-discuss] ZFS compression on Clearcase
On 4 Feb 2010, at 16:35, Bob Friesenhahn wrote: On Thu, 4 Feb 2010, Darren J Moffat wrote: Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. That is FUD generation in my opinion and being overly cautious. The whole point of the POSIX interfaces to a filesystem is that applications don't actually care how the filesystem stores their data. Clearcase itself implements a versioning filesystem so perhaps it is not being overly cautious. Compression could change aspects such as how free space is reported. I'd also like to echo Bob's observations here. Darren's FUDFUD is based on limited experience of ClearCase, I expect ... I do know how ClearCase works and it works *above* the POSIX layer in ZFS - at the VFS layer (and higher). [I've debugged Solaris crash dumps with the clear case kernel modules loaded in them in the past]. By FUD I don't mean it is wrong, but without information about a bug or observed undesirable behaviour it is coming across as Fear that there could be problems. Basically we need more data. What I was pointing out is that because of the layer that ClearCase works there should be no problems - I'm not saying there aren't any just that I don't see where they would be. If there are problems with ZFS then bugs should be logged, leaving statements like ISV x doesn't support using feature f of ZFS is harm full to the ISV's product and to ZFS when there is no bug logged or data about why there is a problem. -- Darren J Moffat ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
On 04/02/2010 11:54, Roshan Perera wrote: Anyone in the group using ZFS compression on clearcase vobs? If so any issues, gotchas? There shouldn't be any issues and I'd be very surprised if there was. IBM support informs that ZFS compression is not supported. Any views on this? Need more data on why the claim it isn't supported - what issue have they seen or do they thing there could be. I see no reason that ZFS compression wouldn't be supported, in fact Clearcase shouldn't even be able to tell. Compression in ZFS is completely below the POSIX filesystem layer and completely out of the control of any application or even kernel service like NFS or CIFS that just uses POSIX interfaces. Same is true of deduplication and will be true of encryption when it integrates as well. -- Darren J Moffat ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
Hi Darren, Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. Thanks Roshan - Original Message - From: Darren J Moffat darr...@opensolaris.org Date: Thursday, February 4, 2010 11:59 am Subject: Re: [zfs-discuss] ZFS compression on Clearcase To: Roshan Perera roshan.per...@sun.com Cc: zfs-discuss@opensolaris.org On 04/02/2010 11:54, Roshan Perera wrote: Anyone in the group using ZFS compression on clearcase vobs? If so any issues, gotchas? There shouldn't be any issues and I'd be very surprised if there was. IBM support informs that ZFS compression is not supported. Any views on this? Need more data on why the claim it isn't supported - what issue have they seen or do they thing there could be. I see no reason that ZFS compression wouldn't be supported, in fact Clearcase shouldn't even be able to tell. Compression in ZFS is completely below the POSIX filesystem layer and completely out of the control of any application or even kernel service like NFS or CIFS that just uses POSIX interfaces. Same is true of deduplication and will be true of encryption when it integrates as well. -- Darren J Moffat ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
On 04/02/2010 12:13, Roshan Perera wrote: Hi Darren, Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. That is FUD generation in my opinion and being overly cautious. The whole point of the POSIX interfaces to a filesystem is that applications don't actually care how the filesystem stores their data. UFS never had checksums before but ZFS adds those, but that didn't mean that applications had to be checked because checksums were now done on the data. What if it was the disk drive that was doing the compression ? There would be similarly no way for the application to actually know that it is happening. What about every other feature we add to ZFS ? Like dedup (which is a type of compression) - again they app can't tell. Or snapshots - the app can't tell. Thats my opinion though and I know that ISVs can be very cautious about new features sometimes and overly so when it is far below their parts of the stack. Taking another example it would be like an ISV that supports their application running over NFS saying they don't support a certain type of vendors switch in the network because they haven't tested it. -- Darren J Moffat ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
Hi Darren, I totally agree with you and have raised some of the points mentioned but you have given even more items to pass on. I will update the alias when I hear further. Many Thanks Roshan - Original Message - From: Darren J Moffat darr...@opensolaris.org Date: Thursday, February 4, 2010 12:42 pm Subject: Re: [zfs-discuss] ZFS compression on Clearcase To: Roshan Perera roshan.per...@sun.com Cc: zfs-discuss@opensolaris.org On 04/02/2010 12:13, Roshan Perera wrote: Hi Darren, Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. That is FUD generation in my opinion and being overly cautious. The whole point of the POSIX interfaces to a filesystem is that applications don't actually care how the filesystem stores their data. UFS never had checksums before but ZFS adds those, but that didn't mean that applications had to be checked because checksums were now done on the data. What if it was the disk drive that was doing the compression ? There would be similarly no way for the application to actually know that it is happening. What about every other feature we add to ZFS ? Like dedup (which is a type of compression) - again they app can't tell. Or snapshots - the app can't tell. Thats my opinion though and I know that ISVs can be very cautious about new features sometimes and overly so when it is far below their parts of the stack. Taking another example it would be like an ISV that supports their application running over NFS saying they don't support a certain type of vendors switch in the network because they haven't tested it. -- Darren J Moffat ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
On 4 Feb 2010, at 16:35, Bob Friesenhahn wrote: On Thu, 4 Feb 2010, Darren J Moffat wrote: Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. That is FUD generation in my opinion and being overly cautious. The whole point of the POSIX interfaces to a filesystem is that applications don't actually care how the filesystem stores their data. Clearcase itself implements a versioning filesystem so perhaps it is not being overly cautious. Compression could change aspects such as how free space is reported. I'd also like to echo Bob's observations here. Darren's FUDFUD is based on limited experience of ClearCase, I expect ... On the client side, ClearCase actually presnets itself as a mounted filesystem, regardless of what the OS has under the covers. In other words, a ClearCase directory will never be 'ZFS' because it's not ZFS, it's ClearCaseFS. On the server side (which might be the case here) the way ClearCase works is to represent the files and contents in a way more akin to a database (e.g. Oracle) than traditional file-system approaches to data (e.g. CVS, SVN). In much the same way there are app-specific issues with ZFS (e.g. matching block-sizes, dealing with ZFS snapshots on a VM image and so forth) there may well be some with ClearCase. At the very least, though, IBM may just be unable/willing to test it at the time and put their stamp of approval on it. In many cases for IBM products, there are supported platforms (often with specific patch levels), much like there are offically supported Solaris platforms and hot-fixes to go for certain applications. They may well just being cautious in what there is until they've had time to test it out for themselves - or more likely, until the first set of paying customers wants to get invoiced for the investigation. But to claim it's FUD without any real data to back it up is just FUD^2. Alex ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS compression on Clearcase
On 04/02/2010 12:42, Darren J Moffat wrote: On 04/02/2010 12:13, Roshan Perera wrote: Hi Darren, Thanks - IBM basically haven't test clearcase with ZFS compression therefore, they don't support currently. Future may change, as such my customer cannot use compression. I have asked IBM for roadmap info to find whether/when it will be supported. That is FUD generation in my opinion and being overly cautious. The whole point of the POSIX interfaces to a filesystem is that applications don't actually care how the filesystem stores their data. I agree (*). It is very similar to what EMC did some years ago by officially stating that while ZFS is supported on their disk arrays ZFS snapshots are not. Even more funny. (*) - however compression is not entirely transparent in such a sense that a reported disk space usage might not be exactly what application expects. But I'm not saying it is an issue here - I honestly don't know. -- Robert Milkowski http://milek.blogspot.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
