Re: New features?
Thanks for this Neil, good to know that most of what I would like is already available. I think your reply highlights what I almost put in there as my first priority: documentation, specifically a HOWTO. > I believe that 2.6.18 has SATA hot-swap, so this should be available > know ... providing you can find out what commands to use. Exactly! > > 2 Adding new disks to arrays. Allows incremental upgrades and to take > > advantage of the hard disk equivalent of Moore's law. > > Works for raid5 and linear. Raid6 one day. Am I misinterpreting the mdadm 2.5 man pages when it says: Grow (or shrink) an array, or otherwise reshape it in some way. Currently supported growth options including changing the active size of component devices in RAID level 1/4/5/6 and changing the number of active devices in RAID1. > > 3. RAID level conversion (1 to 5, 5 to 6, with single-disk to RAID 1 a > > lower priority). > > A single disk is large than a RAID1 built from it, so this is > non-trivial. What exactly do you want to do there. Single to disk is less important, but adding a third disk to a RAID1 pair to make a RAID5 would be nice as would be adding one or more disks to a RAID5 to make a RAID6. John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
New features?
All this discussion has led me to wonder if we users of linux RAID have a clear consensus of what our priorities are, ie what are the things we really want to see soon as opposed to the many things that would be nice but not worth delaying the important things for. FWIW, here are mine, in order although the first two are roughly equal priority. 1 "Warm swap" - replacing drives without taking down the array but maybe having to type in a few commands. Presumably a sata or sata/raid interface issue. (True hot swap is nice but not worth delaying warm- swap.) 2 Adding new disks to arrays. Allows incremental upgrades and to take advantage of the hard disk equivalent of Moore's law. 3. RAID level conversion (1 to 5, 5 to 6, with single-disk to RAID 1 a lower priority). 4. Uneven disk sizes, eg adding a 400GB disk to a 2x200GB mirror to create a 400GB mirror. Together with 2 and 3, allows me to continuously expand a disk array. (Not knowing the code, I wonder if 2, 3 and 4 could be accomplished by allowing an "external" RAID device to have several internal devices and with changes accomplished the old one to shrink and the new one to grow until the old one no longer exists.) Thanks for listening. John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Two-disk RAID5?
> Sorry, I couldn't find a diplomatic way to say you're completely wrong. We don't necessarily expect a diplomatic way, but a clear and intelligent one would be helpful. In two-disk RAID5 which is it? 1) The 'parity bit' is the same as the datum. 2) The parity bit is the complement of the datum. 3) It doesn't work at a bit-wise level. Many of us feel that RAID5 looks like: parity = data[0]; for (i=1; i < ndisks; ++i) parity ^= data[i]; which implies (1). It could easily be (2) but merely saying "it's not data, it's parity" doesn't clarify matters a great deal. But I'm pleased my question has stirred up such controversy! John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: RAID-related: SATA disk removal?
Your error output looks just like what I got on my screen when I just removed the disk. Did you try removing it from the arrays first? Basically warm-swap. Google suggests one or two people have tried it. John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RAID-related: SATA disk removal?
I am testing a machine with two SATA drives in startech.com removable caddies. Everything including swap is RAID1. (I'm running x86_64 Scientific Linux 4.2, a RedHat enterprise clone.) Informal tests suggest that pulling out an active disk causes the whole machine to hang up but removing a disk from the RAID arrays and pulling it out gives the message: "nv_sata: Primary device removed" and everything happily keeps running. Is this a fair description? In practise do people find that following the above allows a failed disk to be replaced without shutting down the machine? Thanks John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Two-disk RAID5?
I'm about to create a RAID1 file system and a strange thought occurs to me: if I create a two-disk RAID5 array then I can grow it later by the simple expedient of adding a third disk and hence doubling its size. Is there any real down-side to this, such as performance? Alternatively is it likely that mdadm will soon be able to convert a RAID1 pair to RAID5 any time soon? (Just how different are they anyway? Isn't the RAID4/5 checksum just an OR?) Thanks John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Re[2]: Concept problem with RAID1?
A much nicer way to get that sort of reliability would be for RAID6 to periodically scan the blocks on the device and to use the extra information to do ECC (and for RAID5 to at tell syslog). John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
