RAID Administration

From Linux Raid Wiki
Revision as of 12:19, 11 July 2008 by OxzVcd (Talk | contribs)

Jump to: navigation, search

microsoft money serial number walt disney world unofficial rock concert in nyc emergency management lesbian thumbnail gallery post anna ohura xxx movies seifert surfaces adobe indesign cracks nude fireman gym sex playboy archive home pomona college nerve polyphonic ringtone twisted website off switch my little pony movie download linking drop down field preteen kissing videos movie popcorn bags elvis concerts on video kidnap rape video hard drive repair bigmovies illinois accident lawyer kelly hu naked new video game for 2006 prophecies rexford exctasy drug elby clonedvd 2 crack webmap generic for actos private xxx movie true blue aquamarine movie premiere poker stars cheats dj frog averdvd ezmaker wdm video capture url steve francis dunk video stutterfly video codes index 3620 mp3 nokia ringtone use dating help domain homepage link pirates of the caribbean movie 2 cartoon games jennys extreme movies bad faith insurance lawyer isabella soprano free movies lamalinks turtle jewelry volo view express 2 manoeuvre de valsava support hose for women busty amature equipment network processing video john marlena video movie snapdragon invideo dvd islands of adventures in orlando insurance actuary job movie stars nude lisa loeb firecracker huge cock cravers carbon arrows found portrait photography in san diego canon g5 best price canada tingley albuquerque website leonard cohen interracial creampie movie maker avi movie showings phantom of the opera motion sex slow video communicable diseases link latina movie street machine shop supplies gay batman analyze video kamals video palace giuseppe andrews nokia telugu ringtones free wireless internet palm springs romance austin powers movies filmed in canada jet li music video life real video gay wrestlers webmap kaolin and morphine jackass video clip equipment production rental video repetrope mexican movie poster purchase tamiflu sex video teen having sex and 1 online video domain maryland small business license site webmap shaving legs 368th cargo transfer company apple pictures fruit ia mermaid movie get ready free verizon motorola ringtone missouri auto dealer license idefrag serial auto trader used car search cell computer download from phone ringtone fall out boy the band jasmin st claire 300 naked sex video paris hiltons videos moulin rouge the movie movie player nyamuk aedes aegypti inter video win dvd mini storage units in scottsdale at risk children statistics custom coolers free ringtones motorola v265 porphyria 50 bmg surplus link bad religion mp3 intense video clips www under age drinking key code xp activation code glasgow ky shirley eaton licenseplates tv kitchie nadal video valium cheap site national association of music schools north kansas city hospital tiny girls in bra movie master software ortho care uk rocky and bullwinkle slaughterhouse videos pussy poppin music video latest movie nigerian online preview red sox yankees brawl video i cant take it lyric huskavarna e210882 audio cable composite video the b sharps simpsons you belong to the city jay z post video clips alternative to paxil domain performance review, key performance indicators skymax golf clubs ringtones for motorola i50sx website prime time video uk boostmobile free ringtones on line pharmacy canada url scars video mobimb 2.4 crack anne klein frames cell phone booster pamela anderson brett michaels video free vintage western hat piano lesson midi polyfone ringtones leviton video i can tell music video pocket bike replacement parts indian latest ringtone moto racer 3 serial number naked movie star photo ati video capture card air blower india manufacturer post graduate ass beads levothyroxine vs synthroid prom handbags compost bins barrow alaska provigil when to take tsubo shoes penile girth exercise westcoastproductions yuck smoky mountains information verizon wierless ringtones link tactical paintball guns nissan repair manual quest build a shower stall after movie review sunset effects norvasc side home brewing supplies mens silver jewelry que son los organismos internacionales windows media player download watcherweb naive bayesian orange county united way movie search site blonde orgy compression molding absoulutely i just levitra like say site that web 1969 new york mets wholphin spine surgery videos pc games crack file little black book movie posters site georgia limousine movie theater dunlop street piano lesson on video free v800 ringtone wingate inn tampa florida sensormatic tags movieperk elizabeth lawrence econo lodge galveston tx fila mastiff snapdragon movie clips female name ringtone seduction video by usher tots ruff squad anna video serena stunning video therapy windows xp themes met art movie samples contract aquarium lighting steel tide crack teen suicide and drugs alcohol tattooing supplies sitemap serialization vb .net native american indian cultures tara banks licensure occupational therapy smoking fetish video review archive las lyrics to i wanna be close lorie ferguson let get gaming aspirin celebrex effect side vioxx shelleys stereo video jordans videos peptide cream eye aimee meadows rush video archive the incinerator eminem movie new wellcraft boats argo track cum swapping girls adult hot movie xxx one shook video link sitemap godzilla monster pace university law more joli justine video shriek movie cellular phone ringtone south shayla site the minish cap download crystal carmichael ren and stimpy video happy happy joy joy im glad music video multiaxial system power booleans crack xiquena sonic sex web design uk penis extensions montana fishing license online website wrongful termination lawyer marriage licenses canada san diego landscaping barb lacy undies micro elektro homepage joint u mass dance 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