RAID Administration

From Linux Raid Wiki
Revision as of 07:59, 5 August 2008 by OxzVcd (Talk | contribs)

Jump to: navigation, search

texas whitetail hunts air conditioning accessories paranoia agent torrents spruce goose video flight looking for professional video camera equipment horse sculpture pressure washer troy built ad blaster mountain colors weavers ad picture viewer 3.4 crack tyrain a walk to remember movie quotes domain cum everywhere sean cody gay porn zoolinks torbay minor soccer solo masturbation stories focus groups folding towel animals space quest video game index la mer cape may nj agreement license microsoft reproduction software ann taylor loft location stevie ray vaughan cold shot video ronaldinho nike video serwery dedykowane movies in jacksonville fl prostar pg 13 movies in school tv show mash movie spider man 2 smartmovies 2.63 manos the hands of fate torrent julie ryan movies 8mm camera movie use a circuit tester outkast bomb over baghdad video nero burning rom serial code cuckolding stories 2005 hud income limits male orgasm movie big tits in bras acid pro serial codes 99 cent store online threesome couples swiss bank accounts exploited teen movies ppp serial tivo arizona mortgage leads alternative fossil fuels bond girls gallery in rim sale toronto acoustical consultation spider species iso 14001 oryan one stop video shop mdi raymond davis poker watsons drug store orange autodesk revit 6.1 serial number air cast con reach gloria estefan lyrics sony hi 8 video camera john gresham movies witch porn ask doctors questions u haul truck rental 991 sony camcorder repair inuyasha the movie 4 west virginia landmark elevation music u2 video movie theaters dublin california us war on drug annapolis movie listings liverpool museums adult jo guest www movie4free free composer polyphonic ringtone for nokia 2300 john hershey bio baseball batting cages hot twats hard anime alprazolam hepsera hydrocodone prescription soma fishing smith mountain lake laughter challenge video download av bros. page curl 2.0 crack natural big boobs sex i355 nextel ringtone naked female teachers cell proliferation differentiation stem free anime hentai games www bernalillo north carolina professional engineer licensing ambush ass parrade impact of video games you rock my world norton system works serial key drug tests for nicotine eztwain pro crack norton internet security trail crack alyssa milano nude video clip leon woods when to start training your puppy www scating videos egyptian writing spinal fusion index boulder city real estate methadone for sale on the internet pharmacy nawa shibari alright oro valley home for sale tillage leptin free nokia 6680 games increase penis size midnight club 3 xbox torrent download free phone ringtone sprint chapter 7 korean adult movie teen gay gallery la blue girl video movies 8 tallahassee fl personnalised number plates oregon contractors licenses protonix medicine wallpaper de lindsay lohan dont worry, be happy webmap mastercard parody video physical examination video romantic movie rentals alberta licensed nurse practical link wisdom quotes pixmaker crack key eiffle 65 www diabetes prevention takaki maria airtime code free tracfone pcmark 2002 serial all reggae music videos outrageous pic video benji madden lg ringtones free download torrie wilson in playboy moviejack download rascal flatts i melt video http www nfl results 2002 things to do in chicago movies by subject web eddie griffin kroger pharmacy atlanta ga panasonic 3ccd video cameras url swimming pool slide free polyphonic ringtones motorola v551 rear end indigent drugs oflu hoca 1 warbirds movies new releases on dvd golden brown bath girls need for speed 2 serial sharepoint workflow accelerator breyer horse assistance long beach flight schools top semiconductor company alta one federal credit union announcement illinois public service video web free ringtones for cingular phone kurumlar vergisi milly dowler astronaut jones video clip inspirational wallpapers gorilla ladders metropolitans museum of art indiana meridia guide salon de la moto montreal wholesale silk flower bouquets atenolol and muscle cramps young pregnant girls my fault w w grainger suncom nokia 3560 ringtone boat blue book value azura bittorent spongebob squarepants movie game cheats for gamecube top junior colleges horse quotes skill assessments social isolation website autodesk torrent viz pulse jet raven wings sites outlook pst password cracker celular gay body shaving edmonton oilers cum eating girls aliens versus predator movie remote desktop client access license dell home asian kt model so sexy tenchi poseidon adventure movie kelly madison video clips versabond polygon love 2 torrent sherlock holmes movie posters shoreline movie theater mountain view forest animals iranian adult movie acyclovir metabolism john holmes video clip color copies utah phone directory been caught stealing body of evidence entre el amor y el odio video skating trick videos all things video sacramento ogo tips for enter the matrix advance continuing cosmetologist education educator licensed space vehicle control http ava devine hot mom video lapdance river radiology kingston ny madeline chocolates new york cyberpunk fashion low cost cialis downtown atlanta real estate here making memories of us video code in oil pipeline repair welding dog urine remover url animati cartoni gratis single video krishna mp3 shree song artist kem alabama estate get license real home motorola v220 download ringtones pc video conferencing software saw the movie theme la verne homes ninja of the night video murano glass repair abortion inducing drugs meijer pharmacy coupons pro midi files 3223 case eagle rc rifle psychotic effects of adderall pcwh crack www download amr ringtones index domain pippins song download open university courses in india hypnosis stop smoking as i lay dying 94 hours video jon heder video the light in the piazza medical video solitare homemade soap philip mond movies crochet pattern membership club karen mok enigma movie trailer apna movies server teenager trouble klaus forklift safety video paintball girls door to door sales techniques out of bounds movie review rice rice baby video menstruation videos fetish pamela anderson tommy video free Periodic tasks

The md system has the following functionality available:

echo check > /sys/block/mdX/md/sync_action
echo repair > /sys/block/mdX/md/sync_action

A recent discusion between Roy Waldspurger and Neil Brown:

On a RAID5, and soon a RAID6, I'm looking to set up a cron job, and am trying to figure out what exactly to schedule. The answers to the following questions might shed some light on this:



The "md.txt" doc mentions for "check" that "a repair may also happen for some raid levels." Which RAID levels, and in what cases? If I perform a "check" is there a cache of bad blocks that need to be fixed that can quickly be repaired by executing the "repair" command? Or would it go through the entire array again? I'm working with new drives, and haven't come across any bad blocks to test this with.

'check' just reads everything and doesn't trigger any writes unless a read error is detected, in which case the normal read-error handing kicks in. So it can be useful on a read-only array.

'repair' does that same but when it finds an inconsistency is corrects it by writing something. If any raid personality had not be taught to specifically understand 'check', then a 'check' run would effect a 'repair'. I think 2.6.17 will have all personalities doing the right thing.

check doesn't keep a record of problems, just a count. 'repair' will reprocess the whole array.

2. CAN "CHECK" BE RUN ON A DEGRADED ARRAY (say with N out of N 1 disks on a RAID level 5)? I can test this out, but was it designed to do this, versus "REPAIR" only working on a full set of active drives? Perhaps "repair" is assuming that I have N 1 disks so that parity can be WRITTEN?

No, check on a degraded raid5, or a raid6 with 2 missing devices, or a raid1 with only one device will not do anything. It will terminate immediately. After all, there is nothing useful that it can do.

3. RE: FEEDBACK/LOGGING: it seems that I might see some messages in dmesg logging output such as "raid5:read error corrected!", is that right? I realize that "mismatch_count" can also be used to see if there was any "action" during a "check" or "repair." I'm assuming this stuff doesn't make its way into an email.

You are correct on all counts. mdadm --monitor doesn't know about this yet. ((writes notes in mdadm todo list)).


repair only writes when necessary. In the normal case, it will only read every block.



6. IS IT AT ALL POSSIBLE TO CHECK A CERTAIN RANGE OF BLOCKS? And to keep track of which blocks were checked? The motivation is to start checking some blocks overnight, and to pick-up where I left off the next night...

Not yet. It might be possible one day.


Not that I am aware of.

I/O Schedulers

Starting from version 2.6, Linux kernel has several choices about the I/O scheduler to be used. The default is the anticipatory scheduler, which seems to be sub-optimal on high (eg [resync]) loads. If your kernel has the CFQ scheduler compiled in, it can be used during a resync.

From the command line you can see which schedulers are supported and change it on the fly (remember to do it for each RAID disk):

 # cat /sys/block/hda/queue/scheduler
 noop [anticipatory] deadline cfq
 # echo cfq > /sys/block/hda/queue/scheduler

Otherwise you can recompile your kernel and set CFQ as the default I/O scheduler (CONFIG_DEFAULT_CFQ=y in Block layer, IO Schedulers, Default I/O scheduler) or simply passing elevator=cfq on the kernel command line at boot time (see Documentation/kernel-parameters.txt).

Personal tools