On Fri, 17 Aug 2007 17:42:55 -0400 Vivek Khera wrote: > I have a shiny new big RAID array. 16x500GB SATA 300+NCQ drives > connected to the host via 4Gb fibre channel. This gives me 6.5Tb of > raw disk.
> I've come up with three possibilities on organizing this disk. My > needs are really for a single 1Tb file system on which I will run > postgres. However, in the future I'm not sure what I'll really need. > I don't plan to ever connect any other servers to this RAID unit. > The three choices I've come with so far are: > 1) Make one RAID volume of 6.5Tb (in a RAID6 + hot spare > configuration), and make one FreeBSD file system on the whole > partition. > 2) Make one RAID volume of 6.5Tb (in a RAID6 + hot spare > configuration), and make 6 FreeBSD partitions with one file system > each. > 3) Make 6 RAID volumes and expose them to FreeBSD as multiple drives, > then make one partition + file system on each "disk". Each RAID > volume would span across all 16 drives, and I could make the volumes > of differing RAID levels, if needed, but I'd probably stick with RAID6 > +spare. > I'm not keen on option 1 because of the potentially long fsck times > after a crash. > What advantage/disadvantage would I have between 2 and 3? The only > thing I can come up with is that the disk scheduling algorithm in > FreeBSD might not be optimal if the drives really are not truly > independent as they are really backed by the same 16 drives, so > option 2 might be better. However, with option 3, if I do ever end > up connecting another host to the array, I can assign some of the > volumes to the other host(s). > My goal is speed, speed, speed. Seems that RAID[56] may be too sloooow. I'd suggest RAID10. I have 6 SATA-II 300MB/s disks at 3WARE adapter. My (very!) simple tests gave about 170MB/s for dd. BTW, I tested (OK, very fast) RAID5, RAID6, gmirror+gstripe and noone get close to RAID10. (Well, as expected, I suppose). > I'm running FreeBSD 6.2/amd64 and > using an LSI fibre card. If you have time you may do your own tests... And in case RAID0 you shouldn't have problems with long fsck. Leave a couple of your disks for hot-swapping and you'll get 7Tb. ;-) > Thanks for any opinions and recommendations. WBR -- bsam _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
