Good point, but the OP wanted to be able to put his md array to sleep, and the next poster just said to use USB for everything .. then what you suggest won't work for him. Once you put /var, /dev, (/tmp perhaps?), back onto his md array, then there is no way he will be able to accomplish his goal of spinning down those disk drives. This is what the OP should do. Buy one of those industrial solid-state flash modules designed to plug into the IDE connector on the motherboard. They appear as a standard ATA disk drive, and are designed for exactly this job. They are solid-state, so you don't need to worry about bad blocks, meaning no need for md. (But like anything, chips can fail, so there is still that single point of failure). All of the SAN/NAS appliance vendors who took my advice and incorporated this strategy are quite happy and this added a great deal of flexibility, as it means that they didn't have to carve out a slice of remaining disks for an O/S image. Then just tweak a few things to take advantage of soft links & the ramdisk filesystem for temporary files & scratch space, and such, and you get some real performance boosts. It really is an elegant solution that many people should consider as general practice. For less than the price of a disk drive, put the O/S on SSD, then use md exclusively for applications. - David @ SANtools ^ com -----Original Message----- From: Michael Tokarev [mailto:mjt@xxxxxxxxxx] Sent: Saturday, May 03, 2008 3:19 AM To: David Lethe Cc: berk walker; Bill Davidsen; Greg Cormier; linux-raid@xxxxxxxxxxxxxxx Subject: Re: Sleeping hard drives in an array? David Lethe wrote: [] > USB for root?? > Bad bad bad bad idea .. unless you get the industrial flash memory. The > typical max number of writes for consumer-grade USB flashdrives is > around 25,000 ... but the low end of the range is 10,000 writes. Why do you think root filesystem will be written that often? Here, / is mounted read-only.. And it changes only when you change some configs... So, root (and /usr) are ok for flash. Just don't put /dev on it (udev/whatever works), and don't put volatile filesystems like /var there too. /mjt -- 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
