Xref: alice comp.databases.oracle.misc:46599 comp.databases.oracle.server:73533 Path: alice!news-feed.fnsi.net!newsfeed.direct.ca!newsfeed.berkeley.edu!newsfeed1.earthlink.net!uunet!lax.uu.net!pao.uu.net!fox.almaden.ibm.com!rtpnews.raleigh.ibm.com!soupjrc From: soupjrc@emily.tampa.advantis.com (John R. Campbell) Newsgroups: comp.databases.oracle.misc,comp.databases.oracle.server,comp.unix.aix,ibm.software.commserver.aix Subject: Re: Perfomance problem with LV mirroring Date: 11 Nov 1999 14:50:46 GMT Organization: IBM Global Services, South, RTP, NC, US Lines: 37 Message-ID: References: <806243$t02$1@porthos.nl.uu.net> <807frb$kea$1@nnrp1.deja.com> <809vd4$qin$1@news1.skynet.be> Reply-To: soupjr@us.ibm.com X-Newsreader: slrn (0.8.5) On Tue, 9 Nov 1999 21:14:58 +0100, "GDN" wrote: >If you have a lot of I/O, the SSA architecture can become a bottleneck. All >the data from the SSA-disks have to come across the same wire. Also you >don't have any caching. If you're not doing the HACMP thing you can always get the 32MB fast-write card for the SSA controller. The following assumes that you're not using RAID5... ...and not using HACMP... If you've got (say) 8 drives and one SSA card, subdivide the loop into 2 4-drive loops, giving you the ability to address 4 drives simultaneously (the SSA controller attempts dual access via the 2 legs of the loop). If you've REALLY got a need for speed you can cheat- get a second SSA card and build 4 loops of 2 drives, giving you 40MB access to each drive at all times... (OK, so you spend more money, but, hey, this is "take no prisoners time". You also waste half of the slots in the 7133 box.) There are also some IBM pubs that describe various ways to place the drives for tuning- none of which I have seen, much less read. (Is this an adequate disclaimer?) When you get into something much bigger, well, things get more sticky and you have to make some more compromises- though (8) 36GB drives in a 7133 cabinet accessed in 4 loops via two SSA cards will feel pretty good. -- John R. Campbell Speaker to Machines soup@jtan.com - As a SysAdmin, yes, I CAN read your e-mail, but I DON'T get that bored! Disclaimer: All opinions expressed are those of John Campbell alone and do not reflect the opinions of his employer(s) or lackeys thereof. Anyone who says differently is itching for a fight!