Hi Subodh, Sorry, but I think you have it backwards - the OS block size must be equal to or smaller than the DB block size: From http://public.dhe.ibm.com/partnerworld/pub/whitepaper/162b6.pdf: "put the data files on one or more file systems with the agblksize equal to the smallest database block size that is used for table spaces in data files on that file system, or 4096, whichever is smallest" In my case, I've got an 8k db_block_size and am using the default OS blocksize of 4k for my data files, and I have my online redo logs on a separate file system with agblksize=512 and both of those are working fine - no problems or questions there. My question is only for the archive logs specifically. Oracle says not to put archive logs on a CIO file system, but why?!? Thanks, Brandon From: Subodh Deshpande [mailto:deshpande.subodh@xxxxxxxxx] OS block size should be multiple of oracle db block size while installing db usually I keep this ratio as 1:2 i.e. if my os block size is 4096 then my oracle block size will be 2048 ________________________________ Privileged/Confidential Information may be contained in this message or attachments hereto. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.