I LOVE RAID 5!!!!!!!!!!!!!!!!!!!!!

ALL RIGHT. Now I've got your attention, please ignore the subject line. What I need to know (in order to overrule an IT manager who is determined to install a RAID setup and won't listen to any arguments against) is exactly WHAT the disadvantages / advantages are between using RAID and JBOD. I tried earlier but the only reply I got was from one Mr. O. Clown (thanx, btw). I think I need to push JBOD but there's a huge difference between gut feeling and reasoned debate. Exactly why does Art hate RAID 5 so much? He keeps saying NO RAID 5! NO RAID 5! etc. ad nauseam but WHY? TIA MAlc Sent via Deja.com http://www.deja.com/ Before you buy.

Try this: http://www.smooth1.demon.co.uk/ifaq06.htm#6.58 and http://www.iiug.org/members/cdi_archive/search.html In article <8toroi$ita$1@nnrp1.deja.com>, malc_p@my-deja.com wrote: > ALL RIGHT. Now I've got your attention, please ignore the subject line. > What I need to know (in order to overrule an IT manager who is > determined to install a RAID setup and won't listen to any arguments > against) is exactly WHAT the disadvantages / advantages are between > using RAID and JBOD. I tried earlier but the only reply I got was from > one Mr. O. Clown (thanx, btw). > I think I need to push JBOD but there's a huge difference between gut > feeling and reasoned debate. > Exactly why does Art hate RAID 5 so much? He keeps saying NO RAID 5! NO > RAID 5! etc. ad nauseam but WHY? > > TIA > > MAlc > > Sent via Deja.com http://www.deja.com/ > Before you buy. > Sent via Deja.com http://www.deja.com/ Before you buy.

I've just returned from a 2 week holiday ( the first in many many years ) to find my production system converted from: 20*9GB JBOD (mirrored) where careful analysis was used to place each and every structure. Refined over time. Honed to an almost Eden of performance. into 4*36Gb RAID5. I cried, looked again, cried, and asked "Aren't the users complaining about performance" (Checkpoints changed from 1 sec (max) to 30sec ave (700sec peak)). reply "Yes, but we thought it may be transient so we thought we'd wait for you to get back" Anyway to answer your question: It is complicated and I can really only discuss writes ( reads someone else will have to raise ). If a write affects one disk exactly then the parity is computed and a write to the affected disk and the parity disk, this is quoted as 50% degradation but it is not quite that bad and I think of it in contexts of a mirrored write. The bad news comes when more than one member disk is affected, and this varies from vendor to vendor etc, but basically each member write causes a read of the parity and a recompute re-write of parity. In simple terms the quoted degradation is 80%. (nasty). When all members are affected the typical approach is to only compute the parity once which yields a degradation of around 20-30%. Cliff (never going on holiday again!) <malc_p@my-deja.com> wrote in message news:8toroi$ita$1@nnrp1.deja.com... > ALL RIGHT. Now I've got your attention, please ignore the subject line. > What I need to know (in order to overrule an IT manager who is > determined to install a RAID setup and won't listen to any arguments > against) is exactly WHAT the disadvantages / advantages are between > using RAID and JBOD. I tried earlier but the only reply I got was from > one Mr. O. Clown (thanx, btw). > I think I need to push JBOD but there's a huge difference between gut > feeling and reasoned debate. > Exactly why does Art hate RAID 5 so much? He keeps saying NO RAID 5! NO > RAID 5! etc. ad nauseam but WHY? > > TIA > > MAlc > > > Sent via Deja.com http://www.deja.com/ > Before you buy.