This message is from the T13 list server.
I am sending this as a test. I haven't been able to get onto the T13 List Server yet although I have been trying to reply to this thread for a while. I apologize if I reawaken the issue. For those who were not at the T13 meeting this week, the original issue has been resolved and hopefully the below clarification will resolve any outstanding ones. ------------------------ [My original, long delayed email] Everyone has made far too big of a deal out of this. First off, FUA doesn't affect queuing or write ordering. The only difference between FUA I/O and other types of I/O is that FUA has the added restriction that the data must be to the medium before the drive can say the transaction is complete. That's it. The drive may still queue the command and handle it however it sees fit. It seems like there should be more to it, but there isn't. Hopefully, you can see that there is no need for concern over overlapped LBA or affects on the queue as it doesn't affect write ordering or the queue. By the way, before too many people decide to jump ship for T10, you will be interested to know that SCSI has had support for FUA for quite some time (See SBC). Many hard drive manufacturers shouldn't have a problem implementing this as much of it can be borrowed from their existing SCSI lines. Nathan -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curtis Stevens Sent: Monday, June 23, 2003 7:39 PM To: T13 List Server Subject: Re: [t13] hmmm.. no comments? This message is from the T13 list server. Gary The wording you propose would defeat the purpose of the command. I do not know if you were there for the discussion. The purpose of the FUA was to cause critical data to be committed to the media, regardless of what is in the que. If you wait for a flush you are delaying the higher priority data. Furthermore, If you know that the area you are writing is for this type of critical data you can prevent the issue you are trying to solve in the drive... Queued FUA is not a function for everyday use, but if you use it for the purpose intended it has great value. Fir instance, if power has been removed from the system and you only have a few MS to store the state, you would wrather not wait for the que to execute or flush, nor would you want to go through the very time consuming process of aborting the que. You simply was the state information committed in the shortest possible time. I see this as one of the main uses for queued FUA commands. --------------------------- Curtis E. Stevens 29 Dewey Irvine, Ca 92620 Home: (949) 552-4777 E-Mail: [EMAIL PROTECTED] The face of a child can say it all, especially the mouth part of the face... ----- Original Message ----- From: "Gary Laatsch" <[EMAIL PROTECTED]> To: "Curtis Stevens" <[EMAIL PROTECTED]>; "T13 List Server" <[EMAIL PROTECTED]> Sent: Monday, June 23, 2003 2:40 PM Subject: Re: [t13] hmmm.. no comments? > Curtis, > > Dropping HDD's is one of those very unsafe thing to do :-) > > My 2 cents on the whole deal is simple. Mark Vallis brought up a very good > point in his example of 2 read requests and the 1 write request in the queue > and than overlapped by a FUA Write request. The current ATAPI-7 spec > indicates that the FUA command shall not be released. Obviously if you do > this, the result is the read data returned is in question (return the old or > new data, the command was recieved before but processed after). Also, the > queued write would request data that should be older then the data just > written with the FUA since the command was actually recieved before. I > think this is really an exception case and should be handled as such. > > My opinion is to modify the wording to the queued FUA commands to add > something like "if the queued FUA request overlaps a previously queued > command, that the queue shall be flushed....blah blah blah" or however we > say it in T13 queue-ish. The biggest issue is that in this case, the FUA > needs to release and it slows down because of the clean up needed to insure > data integrity. But I know that you guys will figure it out this week up > there in SJ. Have fun. > > Gary Laatsch > [EMAIL PROTECTED] > > ----- Original Message ----- > From: "Curtis Stevens" <[EMAIL PROTECTED]> > To: "T13 List Server" <[EMAIL PROTECTED]> > Sent: Monday, June 23, 2003 10:20 AM > Subject: Re: [t13] hmmm.. no comments? > > > > This message is from the T13 list server. > > > > > > I really don't think the issue is one of implementation... It looks to me > > like there are some concerns about usage and the possibility of unexpected > > outcomes. MS clearly stated that they understood several of the > unexpected > > outcomes and still needed the capability. There are many "unsafe" things > > you can do to an HDD, but that has not prevented commands from being > > implemented. > > > > --------------------------- > > Curtis E. Stevens > > 29 Dewey > > Irvine, Ca 92620 > > > > Home: (949) 552-4777 > > E-Mail: [EMAIL PROTECTED] > > > > The face of a child can say it all, especially the mouth part of the > face... > > ----- Original Message ----- > > From: "Eschmann, Michael K" <[EMAIL PROTECTED]> > > To: "T13 List Server" <[EMAIL PROTECTED]> > > Sent: Monday, June 23, 2003 8:23 AM > > Subject: RE: [t13] hmmm.. no comments? > > > > > > > This message is from the T13 list server. > > > > > > > > > My (humble?) opinion is that FUA is necessary and is not dangerous as > long > > as a disk drive properly deals with outstanding requests. > > > > > > First off a flush is very slow, affecting system benchmark scores by as > > much as 5%. The more interesting fact is that not all drives properly > > support flush, where many HDD's will complete the Flush command without > > writing any cached data to media just because of the desire to make ones > > disk synthetically faster than somebody elses. > > > > > > FUA allows the OS to flush critical data without adversely affecting > > performance. The drive should be required to test all outstanding writes > > (in the queued case) and assure that the writes are ordered to guarantee > no > > data loss. Lets take a look at a specific scenario: > > > > > > - Queued write 256 sectors to LBA 10000 > > > - FUA write 1 sector 10001 > > > > > > The 256-sector write must be written to media, or the 1 sector must > > over-write the same sector written by the 256 sector write in the devices > > cache. The drive must also assure that the media results in the same > data. > > I'm sure we could expand this simple case to something much more complex, > > but the basic idea remains: The drive must handle ordering such that > there > > is no data loss. I've asked once before, and I'll ask it again: someone > > offer up a more complex scenario where you believe FUA will break and we > can > > then have a real conversation about the (de)merits of FUA. > > > > > > MKE. > > > > > > > > > > > > -----Original Message----- > > > From: Harlan Andrews [mailto:[EMAIL PROTECTED] > > > Sent: Friday, June 20, 2003 4:47 PM > > > To: Andre Hedrick; Steve Livaccari > > > Cc: Curtis Stevens; T13 List Server; [EMAIL PROTECTED]; Larry Barras > > > Subject: Re: [t13] hmmm.. no comments? > > > > > > > > > This message is from the T13 list server. > > > > > > > > > I have not been present at any of the discussions, but Out-Of-Order > > > writes are inherently dangerous to ANY file system - not only to > > > journaling. Now that we have Flush Cache as a mandatory command, why > > > don't we simply issue the Flush Cache to force unit access. > > > > > > I have not heard any real benefit for such a dangerous operation. Why > > > would anyone even consider it ? > > > > > > ...Harlan > > > > > > on 6/19/03 10:49 PM, [EMAIL PROTECTED] wrote: > > > > > > >This message is from the T13 list server. > > > > > > > > > > > > > > > >Steve, > > > > > > > >This totally nukes and destroys write ordered operations. > > > >Example is the down/commit block on a journalled operation. > > > > > > > >Taking an FUA command to platter and blasting past the queue cache will > > > >destroy every bit of the security designed into any journaling file > > > >system. > > > > > > > >I still do not get why MicroSoft thinks there journaling NTFS of the > > > >meta data in OS buffer cache will not take a hit. If I knew the OS my > > > >data was dependent on did such a "FOOLISH" operation I would find > > another. > > > > > > > >If T13 continues to move towards making it possible for the HOST to do > > bad > > > >things, then the DEVICE is even worse. > > > > > > > >We can all pack our bags and go home and switch to T10, because nobody > > > >will trust a device coming out of T13 again. > > > > > > > >Comments? > > > > > > > >Tomato Shield UP!! > > > > > > > >Andre Hedrick > > > >LAD Storage Consulting Group > > > > > > > >On Wed, 18 Jun 2003, Steve Livaccari wrote: > > > > > > > >> This message is from the T13 list server. > > > >> > > > >> > > > >> > > > >> All modern HDD's have a buffer for write cache that is used to stack > up > > > >> write data from both queued and unqueued write commands. A write > > command > > > >> followed by a flush cache command will likely not move the data from > > the > > > >> last write command to the media until the rest of the data is the > write > > > >> cache is written. If a write FUA command is used the data from the > > write > > > >> FUA command will be given priority over the other data in the write > > cache > > > >> and be written first. > > > >> > > > >> > > > >> > > > >> Regards, > > > >> Steve Livaccari > > > >> > > > >> Hard Drive Engineering > > > >> IBM Global Procurement > > > >> Internet: [EMAIL PROTECTED] > > > >> Phone (919) 543.7393 > > > >> > > > >> > > > >> > > > > > > > > > > >> "Curtis Stevens" > > > > > > > > > > >> <[EMAIL PROTECTED] To: "T13 List > > Server" > > > ><[EMAIL PROTECTED]> > > > >> oo.com> cc: > > > > > > > > > > >> Sent by: Subject: Re: [t13] > > hmmm.. > > > no > > > >comments? > > > >> [EMAIL PROTECTED] > > > > > > > > > > >> rg > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> 06/17/2003 11:09 > > > > > > > > > > >> PM > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > >> > > > >> > > > >> > > > >> This message is from the T13 list server. > > > >> > > > >> > > > >> Gary > > > >> > > > >> As I recall, there were some inacuracies in the proposals as made > > to > > > >> the > > > >> committee. There were many revisions. The only new FUA commands > that > > make > > > >> sense are the queued ones. All others could be followed by flush > > cache. > > > >> > > > >> --------------------------- > > > >> Curtis E. Stevens > > > >> 29 Dewey > > > >> Irvine, Ca 92620 > > > >> > > > >> Home: (949) 552-4777 > > > >> E-Mail: [EMAIL PROTECTED] > > > >> > > > >> The face of a child can say it all, especially the mouth part of the > > > >> face... > > > >> ----- Original Message ----- > > > >> From: "Gary Laatsch" <[EMAIL PROTECTED]> > > > >> To: "Curtis Stevens" <[EMAIL PROTECTED]>; "T13 List Server" > > > >> <[EMAIL PROTECTED]> > > > >> Sent: Tuesday, June 17, 2003 4:40 PM > > > >> Subject: Re: [t13] hmmm.. no comments? > > > >> > > > >> > > > >> > Curtis and Hale, > > > >> > > > > >> > Also, to expand upon this. I think Hale's point is the > proposal > > put > > > >> > forth by Nita didn't contain the QUEUE FUA or QUEUE FUA EXT > commands > > and > > > >> he > > > >> > was wondering where they were added or how they were proposed. My > > memory > > > >> was > > > >> > this was discussed and added at the June 2002 meetings. That is > why > > I > > > >> was > > > >> > wondering if anyone else remembered these discussions. I remember > > > >> > discussing all of this stuff (even Andre's comments about the FUA > > blowig > > > >> > away the queue) but for some reason it just wasn't captured very > well > > in > > > >> the > > > >> > minutes. > > > >> > > > > >> > Gary Laatsch > > > >> > [EMAIL PROTECTED] > > > >> > > > > >> > ----- Original Message ----- > > > >> > From: "Curtis Stevens" <[EMAIL PROTECTED]> > > > >> > To: "T13 List Server" <[EMAIL PROTECTED]> > > > >> > Sent: Tuesday, June 17, 2003 3:15 PM > > > >> > Subject: Re: [t13] hmmm.. no comments? > > > >> > > > > >> > > > > >> > > This message is from the T13 list server. > > > >> > > > > > >> > > > > > >> > > Hale > > > >> > > > > > >> > > I was there during the discussions and there was no secret > > > >> committee. > > > >> > > Basically, MS stated that they wanted to force meta data to the > > drive > > > >> > > without blowing the que. This means that although it is possible > > to > > > >> lose > > > >> > > data, in their application data loss would not occur... > > > >> > > > > > >> > > --------------------------- > > > >> > > Curtis E. Stevens > > > >> > > 29 Dewey > > > >> > > Irvine, Ca 92620 > > > >> > > > > > >> > > Home: (949) 552-4777 > > > >> > > E-Mail: [EMAIL PROTECTED] > > > >> > > > > > >> > > The face of a child can say it all, especially the mouth part of > > the > > > >> > face... > > > >> > > ----- Original Message ----- > > > >> > > From: "Hale Landis" <[EMAIL PROTECTED]> > > > >> > > To: "T13 List Server" <[EMAIL PROTECTED]> > > > >> > > Sent: Tuesday, June 17, 2003 10:57 AM > > > >> > > Subject: [t13] hmmm.. no comments? > > > >> > > > > > >> > > > > > >> > > > This message is from the T13 list server. > > > >> > > > > > > >> > > > > > > >> > > > I'm curious why there are no comments about the question of the > > > >> > > > origin of the WRITE DMA QUEUED FUA command (where is the > > proposal?). > > > >> > > > And why no comments on QUEUED EXT commands with large sector > > counts. > > > >> > > > > > > >> > > > Is this because all these discussions must take place via the > > "secret > > > >> > > > society"? > > > >> > > > > > > >> > > > Hale > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > > *** Hale Landis *** www.ata-atapi.com *** > > > >> > > > > > > >> > > > > > > >> > > > > > >> > > > >> > > > >> > > > >> > > > >> > > > > > >
