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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI Boot Last Call - Technical CommentsMy personal opinion is that an argument is on a very slippery slope when it relies on editing iscsi names vs editing luns. I do not find this mult-OS testing scenario compelling enough to make this change. I dont think Mallikarjun was referring to users looking into PDUs - he was referring to LUN equivalence. Regardless of my personal opinion, I think there are more voices against making the change than in favor. Sincerely, Prasenjit ----- Original Message ----- From: "Mark Bakke" <mbakke@cisco.com> To: "Mallikarjun C." <cbm@rose.hp.com> Cc: "Prasenjit Sarkar" <psarkar@almaden.ibm.com>; "Constantine Sapuntzakis" <csapuntz@stanford.edu>; <ips@ece.cmu.edu> Sent: Wednesday, September 11, 2002 3:29 PM Subject: Re: iSCSI Boot Last Call - Technical Comments > Mallikarjun- > > My comments are embedded. > > -- > Mark > > "Mallikarjun C." wrote: > > > > > consider an application where a host will be able to be booted from > > > a small set of different LUNs, perhaps to change O/S levels in a > > > test environment > > > > How does the DHCP server distinguish which O/S level the client > > wants to boot from, to provide the right LUN in the Root Path? > > The DHCP server doesn't. In this type of environment, the DHCP server > is generally under the control of the same test folks who are booting > the servers. One would manually change the LUN in the DHCP server > GUI or config file, and reboot. The DHCP server doesn't have to do > anything special, but it's one more scenario where the LUN field is > directly manipulated by a user, which is why I'd like to keep it > simple. > > > > If it's a well-known LUN->O/S_rev mapping that the client boot > > code uses by convention, then there's no issue with always leaving > > the LUN field blank (for 0) in the DHCP response. What am I missing? > > > > > I still think that allowing a 16-bit LUN in the string is the > > > simplest, least error-prone approach. > > > > AFAICT, this assumes that the user knows how to figure out which > > 16-bits of the 64-bit LUN are to be entered into the DHCP server > > file. I'm not sure that's a valid assumption. > > > Actually, the user only has to worry about this when the 64-bit LUN > field is used. The 16-bit version always ends up in the high > bytes of the LUN field in the protocol, and the user never sees > this structure, which is really not pretty. I don't think most > users will ever want (or need) to see more than a 16-bit LUN. > > > > My preference is to require 64-bits always (if non-blank), so the boot > > client can simply copy the value in the iSCSI PDUs as-is. > > What customer or user looks at iSCSI PDUs? Would they copy and > paste one from a network analyzer? This doesn't make sense to > me. End users don't care about PDUs. > > > > -- > > Mallikarjun > > > > Mallikarjun Chadalapaka > > Networked Storage Architecture > > Network Storage Solutions > > Hewlett-Packard MS 5668 > > Roseville CA 95747 > > cbm@rose.hp.com > > > > ----- Original Message ----- > > From: "Mark Bakke" <mbakke@cisco.com> > > To: "Prasenjit Sarkar" <psarkar@almaden.ibm.com> > > Cc: "Constantine Sapuntzakis" <csapuntz@stanford.edu>; "Jim Hafner" <hafner@almaden.ibm.com>; "David Black" > > <Black_David@emc.com>; "Duncan Missimer" <duncan_missimer@hp.com>; "Elizabeth Rodriguez" > > <erodrigu@Brocade.COM>; "IPS" <ips@ece.cmu.edu>; "John Hufferd" <hufferd@us.ibm.com>; <owner-ips@ece.cmu.edu> > > Sent: Tuesday, September 10, 2002 2:39 PM > > Subject: Re: iSCSI Boot Last Call - Technical Comments > > > > > It's true that in many cases, zero is all that is needed. However, > > > consider an application where a host will be able to be booted from > > > a small set of different LUNs, perhaps to change O/S levels in a > > > test environment, or to make a different application available > > > on the host. Having these LUNs mapped behind the same iSCSI target > > > and editing the LUN in the root-path string is a lot simpler than > > > having several different targets, and changing the iSCSI name in > > > the root-path. > > > > > > I still think that allowing a 16-bit LUN in the string is the > > > simplest, least error-prone approach. > > > > > > -- > > > Mark > > > > > > Prasenjit Sarkar wrote: > > > > > > > > Mark and Costa, > > > > > > > > If you are so very concerned with entering the value wrong, you can leave > > > > the lun value blank. The lun value defaults to zero and you can always use > > > > lun mapping in the target to make the boot lun to be zero for the initiator. > > > > > > > > Analogous to the other issue you brought up, I think this is going to be the > > > > common case. > > > > > > > > Sincerely, > > > > Prasenjit > > > > > > > > ----- Original Message ----- > > > > From: "Constantine Sapuntzakis" <csapuntz@stanford.edu> > > > > To: "Mark Bakke" <mbakke@cisco.com> > > > > Cc: "Prasenjit Sarkar" <psarkar@almaden.ibm.com>; "Jim Hafner" > > > > <hafner@almaden.ibm.com>; "David Black" <Black_David@emc.com>; "Duncan > > > > Missimer" <duncan_missimer@hp.com>; "Elizabeth Rodriguez" > > > > <erodrigu@Brocade.COM>; "IPS" <ips@ece.cmu.edu>; "John Hufferd" > > > > <hufferd@us.ibm.com>; <owner-ips@ece.cmu.edu> > > > > Sent: Tuesday, September 10, 2002 11:17 AM > > > > Subject: Re: iSCSI Boot Last Call - Technical Comments > > > > > > > > > Many people also use emacs/vi for their configuration too, so they have > > > > > the same problem Mark has with the GUI. I would agree with Mark on his > > > > > point about entry being error-prone. > > > > > > > > > > -Costa > > > > > > > > > > > > > > > Mark Bakke wrote: > > > > > > It would be nice if the GUI could handle this. However, a DHCP > > > > > > GUI (Microsoft, for example), only provides a place to paste in > > > > > > the entire root-path option; it won't give you separate fields > > > > > > to type in the IP address, LUN, and target name. So the user is > > > > > > left with the job of correctly typing in the root-path option. > > > > > > We found (through experience) that the LUN field was particularly > > > > > > frustrating, expecially since a 16-bit LUN value actually appears > > > > > > in the top characters of the LUN field. For example, LUN 12 (hex > > > > > > 0x0c) would appear as: > > > > > > > > > > > > 000c000000000000 > > > > > > > > > > > > in the option string. Getting the wrong number of zeroes before > > > > > > or after either causes the option to be refused by a network boot > > > > > > program, or causes the wrong LUN to be tried. Either way, the > > > > > > user has to decide what the problem is, fix the LUN string, > > > > > > and try again. It's also a bit non-intuitive since most users > > > > > > would expect that the LUN should have been entered as > > > > > > > > > > > > 000000000000000c > > > > > > > > > > > > (BTW, I missed a zero counting that last one, and I caught it > > > > > > because the length looked wrong comparing it to the previous > > > > > > one). > > > > > > > > > > > > Anyway, this is an extremely easy thing to do to make our users' > > > > > > lives easier, and we have no control over adding iSCSI user > > > > > > interface capabilities to DHCP servers. > > > > > > > > > > > > I really think that this is the right thing to do. > > > > > > > > > > > > -- > > > > > > Mark > > > > > > > > > > > > Prasenjit Sarkar wrote: > > > > > > > > > > > >> > > > > > >> > > > > > >> > > > > > >> > > > > > >>Mark, > > > > > >> > > > > > >>I tend to agree with Jim that machines can help with 8-byte entities. > > > > > >> > > > > > >>Regarding the prioritization, I do not doubt that your assertion will > > > > > >>generally hold true, but at the same time, I feel that we should not > > > > make > > > > > >>any assumptions about the order of updates to the Discovery and DHCP > > > > > >>databases in a boot environment. However, if people insist, I can make > > > > the > > > > > >>change. > > > > > >> > > > > > >>Thanks, > > > > > >> > > > > > >> Prasenjit Sarkar > > > > > >> Research Staff Member > > > > > >> IBM Almaden Research > > > > > >> San Jose > > > > > >> > > > > > >> > > > > > >> Jim Hafner > > > > > >> <hafner@almaden.i To: Mark Bakke > > > > <mbakke@cisco.com> > > > > > >> bm.com> cc: Prasenjit > > > > Sarkar <psarkar@almaden.ibm.com>, Duncan > > > > > >> Sent by: Missimer > > > > <duncan_missimer@hp.com>, Costa Sapuntzakis > > > > > >> owner-ips@ece.cmu <csapuntz@stanford.edu>, > > > > Elizabeth Rodriguez > > > > > >> .edu <erodrigu@Brocade.COM>, > > > > David Black <Black_David@emc.com>, > > > > > >> John Hufferd/San > > > > Jose/IBM@IBMUS, IPS <ips@ece.cmu.edu> > > > > > >> Subject: Re: iSCSI Boot > > > > Last Call - Technical Comments > > > > > >> 09/10/2002 07:59 > > > > > >> AM > > > > > >> > > > > > >> > > > > > >> > > > > > >>Mark, > > > > > >> > > > > > >>I would rather not go the route your going with the LUN number issue. > > > > GUIs > > > > > >>can always do the translation to more nibbles under the covers. > > > > Besides, > > > > > >>if you have a LUN that has only 16bits or less of significant (i.e., > > > > > >>nonzero) digits, you'll need to carefully specify where these digits go > > > > in > > > > > >>the 8 byte defined SCSI LUN and that depends on the LUN number > > > > convention > > > > > >>of the target. So, to avoid that can of worms and the extra > > > > descriptions > > > > > >>required, I'd suggest leaving this as an 8byte (16 hex nibble) field. > > > > > >> > > > > > >>On the other point, I have no opinion. > > > > > >> > > > > > >>Jim Hafner > > > > > >> > > > > > >>Sent by: owner-ips@ece.cmu.edu > > > > > >> > > > > > >>To: Prasenjit Sarkar <psarkar@almaden.ibm.com>, Duncan Missimer > > > > > >><duncan_missimer@hp.com>, Costa Sapuntzakis <csapuntz@stanford.edu>, > > > > > >>Elizabeth Rodriguez <erodrigu@Brocade.COM>, David Black > > > > > >><Black_David@emc.com>, John Hufferd/San Jose/IBM@IBMUS, IPS > > > > > >><ips@ece.cmu.edu> > > > > > >>cc: > > > > > >>Subject: iSCSI Boot Last Call - Technical Comments > > > > > >> > > > > > >>I have only a few technical comments on the boot draft. The editorials > > > > > >>have been sent to the authors. The draft looks good! > > > > > >> > > > > > >>Page 4 > > > > > >> > > > > > >> > > > > > >>> The "LUN" field is a hexadecimal representation of the 8-byte LU > > > > > >>> number. Digits above 9 may be either lower or upper case, and all > > > > 16 > > > > > >>> nibbles must be present. If the LUN field is blank, then LUN 0 is > > > > > >>> assumed. > > > > > >> > > > > > >>Since most LUNs are just 16 bits (and many of these are even smaller), > > > > > >>I'd like to relax this a bit. Typing 14 or 15 zeroes plus the actual > > > > > >>LUN value into a field in the DHCP GUI is quite error-prone, since in > > > > > >>a DHCP server's user interface or /etc/dhcpd.conf, this string will be > > > > > >>entered directly by the end user. > > > > > >> > > > > > >>So in addition to the rules above, how about: > > > > > >> > > > > > >>- If the LUN field contains four or fewer hex digits, these digits > > > > > >>constitute the LUN number from which to boot. > > > > > >> > > > > > >>Page 5 > > > > > >> > > > > > >> > > > > > >>> It is possible that the port number obtained from the Discovery > > > > > >>> Service may conflict with the one obtained from the DHCP service. In > > > > > >>> such a case, the implementor has the option to try both port numbers > > > > > >>> in the Boot stage. > > > > > >> > > > > > >>In this case, I think that we should pick one to take precedence, > > > > instead > > > > > >>of leaving it up to the implementor. Since the discovery service should > > > > > >>have the most up-to-date IP address and port number information, I think > > > > > >>that it should be the one that is used. > > > > > >> > > > > > >>-- > > > > > >>Mark A. Bakke > > > > > >>Cisco Systems > > > > > >>mbakke@cisco.com > > > > > >>763.398.1054 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > Mark A. Bakke > > > Cisco Systems > > > mbakke@cisco.com > > > 763.398.1054 > > > > > -- > Mark A. Bakke > Cisco Systems > mbakke@cisco.com > 763.398.1054 >
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