Hi folks, This is going to be one of those corner cases and I'm sure some of you won't even think it a good idea. But I won;t let that stop me from asking your opinion. I'm building a NAS based on a micro-ATX Atom based board (D525MW.) The board has two SATA ports to which I will attach two mirrored 2TB drives form another system. There are 8 USB ports but no other ports to which to attach a boot drive and I had not partitioned the 2 TB drives for another partition. Rather than muck with them, I sought USB boot devices and found prior art on RAIDing USB devices. I purchased 4x 4GB USB flash drives for a grand total of $27 (US) I plan to operate them as a stripe set. I'm not too concerned about reliability, thinking that the USB drives should be pretty reliable if thery're not subject to going through the wash in my pocket. I've done some initial testing (on another PC) and found that striping provides increasing performance even if all of the sticks are on the same USB bus. That surprised me a bit because I expected the USB bus to be a bottleneck, but that does not happen until there are several USB devices active. The particular items that I'd appreciate opinions on are the parameters used to construct the RAID and file system. The guidance I've used so far is found in the following two articles: http://www.analogbit.com/node/4 http://www.analogbit.com/node/13 (I would feel a lot better if the folks here agreed that their selections made sense.) First is partitioning. I used fdisk and default partitioning of one primary partition: =============================================================== root@cypress:~# fdisk -l -c -u /dev/sdb Disk /dev/sdb: 4009 MB, 4009754624 bytes 8 heads, 4 sectors/track, 244736 cylinders, total 7831552 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xf924b0d3 Device Boot Start End Blocks Id System /dev/sdb1 2048 7831551 3914752 fd Linux raid autodetect =============================================================== Next will be to create the RAID using: # mdadm --create /dev/md0 -e 0.9 -n 6 --chunk=64 --level=raid0 /dev/sd[abcd]1 For the file system I saw arguments for and against journaling filesystems for SSD drives. I decided to go with EXT4 Recalculating from the formula in the second article: 'stride' size is numDevice*chunkSize/blockSize => 4*64K/4k => 64 # mkfs.ext4 /dev/md0 -b 4096 -E stride=64 I plan to add noatime to the mount options. (Would relatime be better?) I also plan to put active directories like /tmp and /var/log into RAM via tmpfs. I'll use an OS w/out graphics and have purchased a 2GB RAM stick. I don't plan to use any swap. Alternatives? I could probably boot off the network but that would be less interesting. ;) I could also use RAID5 over the 4 USB drives to guard against a single drive failure. I did try that nut it seemed to sacrifice some throughput. OS will be Ubuntu Server 10.04 (LTS) 32 bit. So... Anything you would do differently? Thanks for your comments. best, hank -- '03 BMW F650CS - hers '98 Dakar K12RS - "BABY K" grew up. '93 R100R w/ Velorex 700 (MBD starts...) '95 Miata - "OUR LC" polish visor: apply squashed bugs, rinse, repeat Beautiful Sunny Winfield, Illinois -- 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
