Messages in this thread | | | Subject | Re: Volume Managers in Linux | Date | Tue, 03 Nov 1998 19:18:14 -0500 | From | "Brandon S. Allbery KF8NH" <> |
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In message <71nrq2$ub7$1@palladium.transmeta.com>, H. Peter Anvin writes: +----- | Followup to: <199811030011.TAA29771@hilfy.ece.cmu.edu> | By author: "Brandon S. Allbery KF8NH" <allbery@kf8nh.apk.net> | In newsgroup: linux.dev.kernel | > | > In message <19981102235619.B1797@quit.mediaways.net>, Florian Lohoff writes | : | > | On Mon, Nov 02, 1998 at 03:57:20PM -0600, Shawn Leas wrote: | > | > provides a way to GRACEFULLY combine multiple physical volumes | > | > into a virtual contiguous logical volume, and gives a STANDARD | > | > interface to applying alocation policies and even RAID. | > | | > | Yep - And even this Ted thought of beeing integrated into the ext234 | > | filesystem | > | > Erk. Logical volume management doesn't belong in the filesystem; it's a | > device-like layer, not a filesystem-like layer. | | Not necessarily. If you want the filesystem to handle devices being | added or even removed, you need some integration into the filesystem. | It may be, though, that some should go into the RAID driver layer. +--->8
I think the filesystem layer needs to communicate more with the driver layer to handle this, but it's not really up to the FS.
A reasonable API should allow any fs to be layered on top of an MD / LVM layer (think of LVM as being a variant of striping); if the fs doesn't know about md a default strategy could be used, but if it's md-aware then the fs can request specific handling for things. If the md layer is sufficiently flexible as to allow variable-sized logical extents (that is, fixed size within a particular logical volume but variable between volumes, presumably always a multiple of the physical extent size), one could (for example) create an md volume and then let "md-aware ext3" designate the use of logical extents the size of cylinder groups. And a log-structured filesystem could request that log extents be allocated on a separate device from file extents if possible.
-- brandon s. allbery [os/2][linux][solaris][japh] allbery@kf8nh.apk.net system administrator [WAY too many hats] allbery@ece.cmu.edu carnegie mellon / electrical and computer engineering KF8NH Kiss my bits, Billy-boy.
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