<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=UTF-8" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> Hi, the (B) part is new to me - I just had my rhce course and they didn´t mention it in any way... Ok, I always do raid in hardware when using servers, for desktop class hardware I prefer doing mirroring. Regarding (A): the 1 GB rebuild rate is a (hp) worst-case szenario when sizing solutions - in fact, it may well be a dozen times faster. Nevertheless, I prefer to think of the worst possible case - in your case, it would be at least 8 hours before the rebuild was done. That would mean 8 hours without protection when using raid5; enough time for the next drive to fail... Furthermore the impact on your CPU will be rather big... Thanks for the info anyway rainer Gilboa Davara wrote: <blockquote cite="mid:1196598334.16346.8.camel@gilboa-work-dev.localdomain" type="cite"> <pre wrap="">On Thu, 2007-11-29 at 21:39 +0100, moi wrote: </pre> <blockquote type="cite"> <pre wrap="">RAID5 (if it really is one) ALWAYS has one drive´s capacity as spare... the spare blocks are just distributed on the disks, thus avoiding the bottleneck of a single spare drive (these would be raid levels 3 and 4). what you meant was RAID6/ADG, a semi-proprietary stuff rather found on hardware controllers, e.g. hp smartarrays. these do calculate a parity for each n blocks, and for "n blocks+parity" generate a second parity block. All these blocks are distributed evenly on all drives in the array. The thing with ADG is the rebuild time - for example the RAIDs at work have about 20 drives each (300 gig); the rebuild time on those is about 1 gb per hour minimum (when there is heavy activity on the raid set). that would mean 300 hours without any protection (when using raid5) ! instead, with raid6/adg there still is one parity left. bad thing, though, is the raid controller has to calculate a lot of parities. furthermore, the cost is rather high with 2 disks´ worth of parity. Most of the time, such setups use RAID10 (mirror and stripe), which uses much cheaper controllers and offers more performance. sorry for off-topic :) </pre> </blockquote> <pre wrap=""> Two remarks: A. Modern RAID5 (be that software and/or hardware controller) build far faster then 1GB/h (291KB/s!??!?!). I timed my own sever (6 250GB drives in software RAID5) at ~12MBps (42GB/h) load and ~90MB/s (324GB/h) idle. B. The Linux kernel has built in software RAID6 support; while slower then the RAID5 implementation, the performance hit is noticeable but not devastating and given the added price (1 250/320/etc GB SATA drive) RAID6 is indeed a fair option if you require two-failed-disk support. - Gilboa </pre> </blockquote> </body> </html>