On Tue, 2007-05-08 at 16:36 +0800, Orlando Andico wrote: > On 5/8/07, Rogelio Serrano <[EMAIL PROTECTED]> wrote: > > > > i dont use hardware raid because it is much slower than software raid. > > and it willingly replicates filesystem blocks with errors. since the > > boot partition is mostly read only thats fine. > > Tell that to people like EMC and Veritas. They seem to have built > entire business models around hardware RAID..
Hi Orly, Clearly EMC and Veritas are good arguments merely by their existence and business success. On the other hand, I'm interested in the original point. *Does* hardware RAID replicate filesystem blocks with errors? The answer is probably "it depends", which is fine. All good answers start with "it depends", but depends on what? Which RAID types does that affect most? I don't have enough experience or theory with RAID to know things like, if you have RAID-1, is one of the mirrors a primary (for read/write) and the second is mostly for replication (read/write too, but preference goes to the primary). Or does the RAID hardware (for RAID-1, anyway) actually randomly choose which half of the mirror to write to and then (possibly) replicate disk errors on that written half to the other half? How about RAID-5, can data errors due to hardware errors propagate with that? Or maybe some RAID controllers detect the error, mark that block bad (at the hardware RAID level, no need to badblocks) and move the data to some other block and replicate that? That might cause its own problems too though, hiding the bug so that drives can slowly degrade and RAID still works and people who think that RAID means they're backed up wake up one day and find themselves in deep shyte. But don't let that verbosity stand in the way of explaining. I don't know enough about the realities of RAID and comparative advantages of different RAID controllers (which brands stand out overall, which families of controller models to stay away from) to actually know what I'm talking about. I'm hoping there'll be discussion here that I can learn from. tiger _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List [email protected] (#PLUG @ irc.free.net.ph) Read the Guidelines: http://linux.org.ph/lists Searchable Archives: http://archives.free.net.ph
