Bernd Walter wrote: ... > One problem is with the data blocks beeing that big, when writing > 512 Byte you effectifly do a read-modify-write of a larger physical > block. > This can be handled quite well with larger FS block. > The much bigger problem is with power loss when writing such a > maintenence block. > You loose a very large area of logical blocks when this fails, > since a 4k maintenence block contains the allocation for several hundert > kB of logical data blocks. > In other words - you possibly loose data blocks that were not written > a long time and the database wouldn't expect a problem with that data. > Even for ZIL it is very questionable if you loose a large data area, > since the purpose is to have the data that was already sinced readable > after a power loss. ... ZFS doesn't suffer from this problem because the design is to always write a new section of data rather than over write "current" data. So if you lose power in the middle of a write to a data block, there is no damage to the old data. DarrenReceived on Sun Dec 16 2007 - 08:40:24 UTC
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