Re: Raw space vs filesystem

Posted in 1997

Doug Johnson — Thu, 09 Jan 1997 13:55:06 -0800 — source: Informix-list mailing list archive (1991-1998)

Dinesh Salegame wrote: > > Hi, > > I wanted to find out what are the pros and cons of using raw vs regular > filesystems for dbspaces. We are using Informix 7.2 and HP UX 10.01. > Any comments on how to use the LVM in this context is greatly > appreciated ! > > thanx > Dinesh > Comnet Int Co. There are also performance considerations for 'raw lvm' vs 'raw devices'. HP-UX lvm breaks large read requests (from RA-PAGES) into multiple 2KB SCSI read CDBs. For example, if RA-PAGES is 32 then Informix issues a single 64KB read request but lvm issues 32 2KB SCSI read CDBs. It's particularly bad if the disk subsystem disconnects after every read, even if the bytes are in a buffer. Doug