Hi Jan, comments below... jan damborsky wrote: > Hi folks, > > I am member of Solaris Install team and I am currently working > on making Slim installer compliant with ZFS boot design specification: > > http://opensolaris.org/os/community/arc/caselog/2006/370/commitment-materials/spec-txt/ > > After ZFS boot project was integrated into Nevada and support > for installation on ZFS root delivered into legacy installer, > some differences occurred between how Slim installer implements > ZFS root and how it is done in legacy installer. > > One part is that we need to change in Slim installer is to create > swap & dump on ZFS volume instead of utilizing UFS slice for this > as defined in design spec and implemented in SXCE installer. > > When reading through the specification and looking at SXCE > installer source code, I have realized some points are not quite > clear to me. > > Could I please ask you to help me clarify them in order to > follow the right way as far as implementation of that features > is concerned ? > > Thank you very much, > Jan > > > [i] Formula for calculating dump & swap size > -------------------------------------------- > > I have gone through the specification and found that > following formula should be used for calculating default > size of swap & dump during installation: > > o size of dump: 1/4 of physical memory >
This is a non-starter for systems with 1-4 TBytes of physical memory. There must be a reasonable maximum cap, most likely based on the size of the pool, given that we regularly boot large systems from modest-sized disks. > o size of swap: max of (512MiB, 1% of rpool size) > > However, looking at the source code, SXCE installer > calculates default sizes using slightly different > algorithm: > > size_of_swap = size_of_dump = MAX(512 MiB, MIN(physical_memory/2, 32 GiB)) > > Are there any preferences which one should be used or is > there any other possibility we might take into account ? > zero would make me happy :-) But there are some cases where swap space is preferred. Again, there needs to be a reasonable cap. In general, the larger the system, the less use for swap during normal operations, so for most cases there is no need for really large swap volumes. These can also be adjusted later, so the default can be modest. One day perhaps it will be fully self-adjusting like it is with other UNIX[-like] implementations. > > [ii] Procedure of creating dump & swap > -------------------------------------- > > Looking at the SXCE source code, I have discovered that following > commands should be used for creating swap & dump: > > o swap > # /usr/sbin/zfs create -b PAGESIZE -V <size_in_mb>m rpool/swap > # /usr/sbin/swap -a /dev/zvol/dsk/rpool/swap > > o dump > # /usr/sbin/zfs create -b 128*1024 -V <size_in_mb>m rpool/dump > # /usr/sbin/dumpadm -d /dev/zvol/dsk/rpool/dump > > Could you please let me know, if my observations are correct > or if I should use different approach ? > > As far as setting of volume block size is concerned (-b option), > how that numbers are to be determined ? Will they be the same in > different scenarios or are there plans to tune them in some way > in future ? > Setting the swap blocksize to pagesize is interesting, but should be ok for most cases. The reason I say it is interesting is because it is optimized for small systems, but not for larger systems which typically see more use of large page sizes. OTOH larger systems should not swap, so it is probably a non-issue for them. Small systems should see this as the best solution. Dump just sets the blocksize to the default, so it is a no-op. -- richard > > [iii] Is there anything else I should be aware of ? > --------------------------------------------------- > Installation should *not* fail due to running out of space because of large dump or swap allocations. I think the algorithm should first take into account the space available in the pool after accounting for the OS. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
