Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wed, May 28, 2008 at 03:36:33PM +0900, Christian Balzer wrote: > > > And you really want to use a resilient approach on the lowest level, > > > in > > > your case RAID5 over the whole disks (with one spare at least given > > > that > > > with 80 drives per node you are bound to have disk failures frequently > > > enough). In fact I'd question the need for having a DRBD mirror of > > > archive backups in the first place, but that is your call and money. > > > ^^ > > > > Unfortunately, cost is driving most of my decisions and RAID5 adds > > 10-20% to the total cost. > Come again? I was suggesting an overhead of 2 drives, which comes to 2.5% > with 80 drives. Other than that RAID5 is free (md driver) and you sure > were not holding back with CPU power in your specs (less, but faster > cores and most likely Opteron instead of Intel would do better in > this scenario). Of course I have no idea how many SATA (scsi really) > drives current kernels can handle and how many drives can be part of a > software RAID. RAID5 might be free (as in md driver), but it surely isn't free as in performance degradation and I think you don't actually want a raid5 of 79 drives... Please read the archives of linux-raid as to what is the recommended raid5 size (as in number of drives); it's definitely below 20. The reason is that two disk failure (out of 79) is quite likely, and then you lose actually the whole 80 drives and you'll have lot of pain resynching. regards, iustin