2016-05-20 22:31 GMT+08:00 John Stoffel <john@xxxxxxxxxxx>: > I wouldn't even think of using hardware RAID in this situation, and > I'd also not think about maximizing the size of the RAID6 volumes as > well, due to rebuild speed penalty. Another issue to think about is > chunk size as the number of members in a RAID array go up. Say you > have the default 64k block size (number pulled from thin air...), so > you need to have N * 64K worth of data before you can write a full > stripe of data. So as your writing data, you'll want to keep the > block size down. thanks for sharing the thought. maybe I should lower the chunk size for full stripe write. > But back to goal. If you're writing large files, since I think NVR > refers to CCTV camera files, please correct me if wrong, you should > just stick with the defaults in terms of RAID defaults. yes NVR refers CCTV files. > What I would do just just create a RAID6 array with 10 disks, so you > only have 8 x 4Tb of data, with two parity disks. Then create another > RAID6 with the remainng 10 disks. Then you would add them as PVs into > LVM, and then stripe acroos them. Something like this: yes I will use lvm to combine the array if necessary. but 10 disks with raid6 will use only 80% of disk capacity. I had use 16 disks before and it seems ok. > # Since you want large space, make the extents use larger chunks here > # in the VG. > vgcreate -s 16 NVR /dev/md100 /dev/md101 thanks for the suggestion. I will study it. > I'd want redundant power supplies, some hot spare disks, a UPS, and a > rock solid hardware with plenty of memory. The other issue is that > unless you run a recent linux kernel, you might run into performance > problems with the RAID5/6 parity calculations being all done on a > single CPU core. Newer versions should have fixed this, but I don't > recall the exact version right now. yes server hardware and environment is ready. > Also, think about backups. With this size of a system, backups are > going to be painful.... but maybe you don't care about backups of NVR > files past a certain time? no backup for this indeed. if the data gone, just let time to re-collect it. thanks again for your sharing!! Regards, tbskyd -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
