[raid 卡] 對 軟硬 Raid /Raid 5 /Raid 6 /Raid Ram 既一堆問題

22over7

我知道 軟raid會用CPU好多資源
硬Raid 一定係用Raid 卡
Raid 5可以容許死一隻hd
Raid 6 則可以容許死2隻
小弟望過下網上一D Raid test
有D test Raid 5 可以上到  8XX MB/s write   (7hd)
但又見有D test Raid 5 只有 2x MB/s write   (4 hd)
請問一下係咪應該係 軟raid(4hd)  同   硬 raid(7hd) 個case  既分別??
又見網上有人話 Raid 5 要有 Raid Ram 同電池,當真??
隻Raid Ram 又要幾大到先ok?
Raid 6又會否更重視Raid  Ram 大少??
請教

melodyayaka

我知道 軟raid會用CPU好多資源
硬Raid 一定係用Raid 卡
Raid 5可以容許死一隻hd
Raid 6 則可以容許死2隻
...
22over7 發表於 2011-1-5 02:18

A better RAID controller will provider better performance during the rebuild process.
I dont see the point to run Software RAID-5 in a production environment

The RAM + battery are for the write-back cache, because the write operation takes time in a RAID-5 setup, using write-back cache will provide better performance (Like Database I/O).
If you dont have a battery to protect the write-back cache, when there is a power lost, you will lost all the data in the cache if they have not yet been written into the disk.

Some high-end raid controller will even provide a CF-CARD to store the cache content in the event of power lost.

airhins

But for home usage, I would like to use MDADM..

Pros
1. Low Cost, (linux)
2. Higher Performance (after turning) -- (RAID5/6 ONLY)

Cons
1. Hard for new users
2. backup for important is a must

22over7

But for home usage, I would like to use MDADM..

Pros
1. Low Cost, (linux)
2. Higher Performance (af ...
airhins 發表於 2011-1-5 15:45

Thank for answering my questions
Before that , I did never heard about MDADM
After some data search , I found out that MDADM is a Software Raid
Thats mean it was just using Sata controller to hold up the Raid
I was wondering does a MDADM Raid could have a better Performance than a Hardware under a same condition?( same HD, Same CPU)
( most of the tests show that software Raid 5/6 only have a very poor performance)
Also, what kind of chipset did MDADM support?

In addiction ,is it possibleto have MDADM working for windows under a dual-OS ( Linux/windows)
Moreover, could you show us some speed test result on MDADM ??

KinChungE

Thank for answering my questions
Before that , I did never heard about MDADM
After some data search ...
22over7 發表於 2011-1-5 16:56

MDADM冇得same cpu比
因為hardware raid用raid card上既processor, 但係MDADM係用system processor (CPU)
任何電腦都可以用MDADM, 只要多過一隻HDD, 裝Linux就可以
dual-OS一齊行就唯有vmware呢類software, 效能一定差

22over7

裝個FREENAS就可以睇會下SOFT RAID5, 我3隻2TB GREED 行GIGA 都有6X MB WRITE
yupennyhk 發表於 2011-1-5 20:36

6xMB write  我接受唔到
所以先想玩HR

   

MDADM冇得same cpu比
因為hardware raid用raid card上既processor, 但係MDADM係用system processor (CPU) ...
KinChungE 發表於 2011-1-5 19:18

咁講法MDADM 都係software Raid.....
都唔會快得去邊啦我估.....
仲一定要用Linux.....行唔到adobe CS5
KinCE 兄 我想問下 Dell 5i 同 Dell 6i
除了6i 有Raid 6 同6i 行 256MB Ram 之外
效能上分別大唔大??
因為我見有人賣5i 連 512 MB Ram  仲平過6i 小小....
256 會唔會唔夠黎行Raid 6 ??

harial

Raid Card ram用黎做cache啫,raid card都係睇下你有幾多budget同做咩野
每張raid卡raid mode support都唔同,行raid 6 建議你玩512mb,但唔建議你用5i

22over7

Raid Card ram用黎做cache啫,raid card都係睇下你有幾多budget同做咩野
每張raid卡raid mode support都唔同 ...
harial 發表於 2011-1-6 16:00

5i 有512MB but 行唔到Raid6
6i 行到Raid6 but 得256 MB ......
Ching 言下之意是否比較建議我入6i??

rkkc

6xMB write  我接受唔到
所以先想玩HR
22over7 發表於 2011-1-6 15:38

樓上是指 NAS 接 gigabit lan 有 6xMByte 寫入速度，gigabit lan 有 500Mbit (6x * 8) 傳送率 50% bandwidth 已很不錯；

soft RAID 本身一定不止那個數 (要在 cmd shell 做測試才知實數)，只是受 gigabit lan 所限去不盡，換了 RAID 咭也快不了；

如果你目的是用 PC 做 NAS，先試 soft RAID 才考慮買 RAID 咭，因為 lan 才是瓶頸位；

不過即使是 Windows desktop 用 RAID，不妨先試 on board RAID (Intel/AMD) 或 Windows dynamic volume RAID。