Darren J Moffat wrote: > John Cecere wrote: > >> The man page for dumpadm says this: >> >> A given ZFS volume cannot be configured for both the swap area and the dump >> device. >> >> And indeed when I try to use a zvol as both, I get: >> >> zvol cannot be used as a swap device and a dump device >> >> My question is, why not ? >> > > Swap is a normal ZVOL and subject to COW, checksum, compression (and > coming soon encryption). > > Would there be no performance benefits from having swap read/write from contiguous preallocated space also?
I do realize that nifty features like encryption might be lost in that case, but I"m wondering if there's any performance to be gained? Then again if you're concerned about performance you need to just buy ram till you stop swapping all together, huh? -Kyle > Dump ZVOLs are preallocated contiguous space that are written to > directly by the ldi_dump routines, they aren't written to by normal ZIO > transactions, they aren't checksum'd - the compression is done by the > dump layer not by ZFS. This is needed because when we are writing a > crash dump we want as little as possible in IO the stack. > > -- > Darren J Moffat > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
