AToL: CLVM & EFI (anglicky)

29.6.2011 11:45 | Přečteno: 1095× | Linux | | poslední úprava: 29.6.2011 11:43

Autor: Lukáš Bezdička
Nasledovný príspevok je študentskou prácou, ktorá vznikla v rámci predmetu Advanced Topics of Linux Administration. Predmet je vypisovaný na Fakulte informatiky MU v spolupráci so spoločnosťou Red Hat Czech. Vyučovacím jazykom je angličtina a preto je v nej aj nasledovný príspevok, študent nemá právo výberu iného jazyka. Komentáre k obsahu príspevku sú vítané v ľubovoľnom zrozumiteľnom jazyku.

LVM

Logical Volume Management adds fast and reliable abstraction layer on top of classical partitions. LVM provides a means to concatenate, stripe together or otherwise combine partitions into larger virtual ones that administrators can re-size or move, potentially without interrupting system use. Logical partitions are not limited to size of physical disks. LVM also allows mirroring and snapshots.

Layout

              +-----------------------------+
              |Logical Volume|Logical Volume|
              |LE|LE|LE|LE|LE|LE|LE|LE|LE|LE|
              |-----------------------------|
              |        Volume Group         |
              |-------------------_---------|
              |   Physical Volume Group     |
              +-----------------------------+
 ___________________________|___________________________
/                          / \                          \
|PE|PE|PE|PE|PE|PE|PE|PE|PE| |PE|PE|PE|PE|PE|PE|PE|PE|PE|
|      Physical Volume     | |      Physical Volume     |
|--------------------------| |--------------------------|
|  HDD or partition or LUN | |  HDD or partition or LUN |
+--------------------------+ +--------------------------+

LVM layout consists of three logical types: Physical Volume, Volume Group, Logical Volume. Physical Volume (PV) represents real hardware - block device (hard disk, partition or LUN). PVs are divided into small pieces - Physical Extents (PE) and can be grouped into groups - Physical Volume Groups (PVG). PVGs are grouped together into Volume Groups (VG) which are divided into small pieces of Logical Extents (LE). LEs grouped together form Logical Volumes (LV). LVs represent raw block devices to running system. Grouping PVs into PVGs allows mapping one LE on more than one PE which allows mirroring, online transferring data on physical devices and so on.

Labels and metadata

PVs are created by putting Label on usually second 512byte sector, but can be on any of first four sectors. Label stores name, uuid, size in bites and location of metadata. Metadata are stored in ASCII, contain configuration information about VG and are identical on each PV in same VG. As metadata copies on huge VGs cause high overhead costs LVN is often used in setup where only original metadata is stored on PV. This is done by providing "metadatacopies 0" option to "pvcreate" on creation of PVs. One can read LVN metadata from raw disk by running "strings /dev/disk | grep "# Generated by LVMA 2048 >output.txt" where metadata size may bigger on big VGs so one has to increase size to 2048+k*1024.

CLVM

Problems start while using LVN on clusters. This comes from multiple access to metadata which has to be resolved by locking mechanism. While high availability clusters don't require locking as only one machine is accessing device at the time it's preferred to use HaLVM and for normal clusters there is solution for locking by using clvmd daemon. CLVM is LVM extension which adds locking of PE during the access.

For CLVM to work with Red Hat Cluster Suite one has to have running cluster and turn on clvmd (chkconfig clvmd on;), change LVM locking mechanism, check that all nodes in cluster have access to PVs and it's done. Work with CLVM is nearly the same as with normal LVM. Change of locking mechanism is done by running "/sbin/lvmconf –enable-cluster" or change in "/etc/lvm/lvm.conf" option "locking = 3" has to be set. By this LVM will use built in dlm mechanism. To check if clvmd is working correctly one can run "cman tool servicies", output should contain "DLM (Distributed Lock Manager) lockspaces - clvmd".

EFI

UEFI (Unified Extensible Firmware Interface) is a specification developed by Intel to become replacement for older BIOS firmware interface in PCs. UEFI is not restricted to any specific processor architecture, and can run on top of or instead of traditional BIOS implementations. EFI is often criticized for adding bigger complexity over the feautres compared to OpenBIOS or Coreboot. UEFI consists of:

GPT

The MBR partitioning system created in 1980s hits it's limitations and inorder to replace it Intel created GPT (GUID Partition Types) as part of EFI. GPT uses logical block addressing (LBA) instead of cylinder/head/sector (CHS). Disk pointers are 64bit allowing 9.4ZB size. Critical GPT data structures are stored twice on the disk: once at the start and again at the end. GPT uses CRC to improve corruption detection. GPT allows 128 partitions and stores them all in single partition table. GPT uses GUIS to identify partition types. GPT also adds partition labels and is somewhat backwards compatible by using "gptsync" to fake MBR. Usual partitioning tool "fdisk" does not support GPT so one has to use "parted" which is more robust and actually should be preferred over fdisk. In parted GPT is turned on by running "mklabel". There should be full support for GPT in modern Linux distributions by now, for example Fedora should boot without problems since F13.

• Disk support - new partitioning scheme with GPT
• Processor support - access to all of the memory in pre-boot environment by removing old BIOS limitations
• Services - boot and runtime services
• Protocols - protocols defining interfaces for communication between binary modules
• Device drivers - EFI provides processor-independent device driver environment (EBC) similar to OpenFirmware
• Boot Management - attempt to remove need for a dedicated boot loader mechanism
• The EFI shell- shell environment to execute EFI applications
• Extensions - ability to load extensions from any non-volatile storage device attached to the computer

Sources

• http://{cs,en}.wikipedia.org/wiki/Logical_Volume_Management
• http://www.howtoforge.com/linux_lvm
• http://www.centos.org/docs/5/html/Cluster_Logical_Volume_Manager/physical_volumes.html
• http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
• http://cs.wikipedia.org/wiki/Extensible_Firmware_Interface
• http://en.wikipedia.org/wiki/GUID_Partition_Table
• https://bugzilla.redhat.com/show_bug.cgi?id=518477
• https://bugzilla.redhat.com/show_bug.cgi?id=604182
• https://bugzilla.redhat.com/show_bug.cgi?id=694808
• https://bugzilla.redhat.com/show_bug.cgi?id=467848
• http://www.ibm.com/developerworks/linux/library/l-gpt/index.html?ca=dgr-lnxw97GPT-Storagedth-lx&S_TACT=105AGY83&S_CMP=grlnxw97

       

Komentáře

[čech]

Táhni s tím anglicky psaným zápisem do hajzlu.

[slovák]

Tak se nauč anglicky kryple a nevotravuj

[Jirka Keresteš]

Tahni tam sam. Porad si tu nekdo stezuje, ze by tu mely byt jenom zapisky souvisejici s linuxem, a kdyz se tu nejaky objevi, tak tu pod nim zacnou pindat anonymove, ze se jim to taky nelibi. Co kdybys treba misto psani hloupych komentaru delal neco uzitecneho? Treba by ses mohl naucit anglicky, urcite se ti to bude hodit

[dad]

podle jmena jsem si hned rekl, ze asi budete cikan. Ale ta perfektni gramatika a logicka stavba vet je pro to etnikum spis netypicka a proto ma otazka, zda mate s cikanama neco spolecneho?

Aby si nekdo nemyslel , ze je to legrace, problematika vzdelanosti cikanu je zasadni otazka, jak tyto spoluobcany ziskat na nasi stranu. Proto ta otazka, zda se zde nejedna o takovy pripad. Pro integraci toho etnika by to bylo uzasne, kdyby se rozkriklo, ze i cikani se podileji na OpenSource aktivitach. Rada lidi by pak zmenila na tyto spoluobcany nazor.

[Jirka Keresteš]

Asi vas zklamu, ale nemam. Mam pouze pribuzne ze Slovenska.

Jinak doporucuji vymenu kristalove koule, protoze tahle zjevne nefunguje.

[AsciiWolf]

+1

[Qerulant]

Co kDyByS TrEbA MiStO PsAnI HlOuPyCh kOmEnTaRu dElAl nEcO UzItEcNeHo? TrEbA By sEs rAdSi mOhL NaUcIt wYpAtLaWaT. xD I aM dIyNg!!! ZhiWOT jE Na nIc

[藍染が]

禿頭から額にかけて大きな十文字の傷を持ち、膝まで垂れる長い髭（自分で結っており、月に一度毛先を揃えている）をたくわえ、好々爺のような容姿をしている。肉体は老人とは思えぬほど鍛え抜かれており、歴戦の老将の証拠として数多くの傷が刻まれている。かなりの老齢（少なくとも二千歳以上）だが自分より強い死神がいないために千年以上も総隊長を務めてきた猛者であり、死神としての実力は未だ衰えることなく、護廷十三隊総隊長を名乗るにふさわしい実力を有し、藍染でさえも「戦闘能力は私より上」と認めている。また、素手での戦闘能力も規格外であり、流刃若火を封じる解放状態のワンダーワイスを素手で倒すほどである。羽裏色は京紫（きょうむらさき）。羽織は袖のあるタイプ。 約二千年前、死神等の教育機関「死神統学院（現在の真央霊術院）」を創設。そこから初の隊長となった京楽、浮竹を我が子のように誇っているが、その彼らであっても自分と道を違えた時には容赦無く断罪する、世界の正義のために非情な決断をする強固な意志を持つ。藍染が中央四十六室のメンバーを殺害したため、現在は一人で中央四十六室と同等の決定権を持つ。 空座町での藍染との決戦にも、他の隊長格を率いる形で参戦。全ての隊長や仮面の軍勢が倒された後で、藍染に挑む中で流刃若火を封じるワンダーワイスを倒すものの、流刃若火の炎を吸収したワンダーワイスが、それを爆発させようとしたのを抑え込むために重傷を負った。しかし、犠牲破道の九十六・一刀火葬を放ち、藍染の隙を作ることに成功する。その為、決戦後は左腕を失っている。 新隊長天貝繍助篇では天貝繍助の父で彼の部下である如月秦戌が雲井尭覚により獏爻刀に手を染めた事を知りやむを得ず殺害する羽目になったため、如月の息子の天貝に恨まれ、命を狙われることになる。 和食全般を好み、洋食を嫌う。月1で隊士達を集めて茶会を開くことが趣味。テレビアニメの「死神図鑑ゴールデン」では、年のためか、人を呼び出しておきながら自分はうっかり寝てしまう、という失態が見られる。

[ہمم]

بھاڑ میں جاؤ

[polymorf]

nandžá koré?

[rastos]

Urobiť copy&paste z webu vie každý

[polymorf]

Googlit vie kazdy

[Limoto]

Kéž by...

[Qerulant]

פסולת

היה טקסט סטנדרטי עוד במאה ה כאשר הדפסה לא ידועה לקחה מגש של דפוס ועירבלה אותו כדיליצורסוג של ספר דגימה. ספר זה שרד לא רק חמש מאות שנים אלא גם את הקפיצה לתוך ההדפסה האלקטרונית, ונותר כמו שהוא ביסודו. ספר זה הפך פופולרי יותר בשנות ה

[pools]

Komentáře su vítané v akolkoviek jazyku hlavně proto, že je nikdo z autorů nečte...

[Marek 'marx' Grác]

Pod poslednými dvoma príspevkami diskutovali aj autori článku

[Lukas BEzdicka]

No miesto toho aby niekto riesil chyby v texte, ci uz obsahove alebo gramaticke tak je tu neuveritelne frflanie na anglictinu. Text bol povodne aspon pseudo snaha na asciiart, original dostupny tu: https://github.com/xbezdick/clvm Poprosim relevantne komentare a hlasenia chyb do issues. Dakujem