# 2.6.29 AMD Hardware RAID not recognized

## SeaHag

I'm booting on the install disc and it shows my individual RAID discs as sda and sdb but I don't see anything about the raid volume. In FreeBSD it's called /dev/ar0, How is it called in Gentoo? I'm new to Gentoo and this is my first install so I'm not sure if I need to load modules or what. What info should I look for or post here?

Foxconn Digitalife A79A-S mbd.

AMD Phenom 9500 quad

SB700 southbridgeLast edited by SeaHag on Fri Jul 10, 2009 4:57 am; edited 1 time in total

----------

## hielvc

Usually you should post " emerge --info ", no need if your on a install CD. Also posting " lspci " and in your case " lsmod " would give us needed info. I did a google  " jmicron jmb362 esata linux" and found this http://www.jmicron.com/Support_FAQ.html which should help. I would recommend using  Main Page - SystemRescueCd. Its based on Gentoo and is update.

----------

## SeaHag

Here's lspci and lsmod after I boot from the install CD:

lspci:

```

00:00.0 Host bridge: ATI Technologies Inc RD790 Northbridge only dual slot PCI-e_GFX and HT3 K8 part

00:02.0 PCI bridge: ATI Technologies Inc RD790 PCI to PCI bridge (external gfx0 port A)

00:06.0 PCI bridge: ATI Technologies Inc RD790 PCI to PCI bridge (PCI express gpp port C)

00:07.0 PCI bridge: ATI Technologies Inc RD790 PCI to PCI bridge (PCI express gpp port D)

00:11.0 RAID bus controller: ATI Technologies Inc SB700/SB800 SATA Controller [RAID5 mode]

00:12.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller

00:12.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller

00:12.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller

00:13.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller

00:13.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller

00:13.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller

00:14.0 SMBus: ATI Technologies Inc SBx00 SMBus Controller (rev 3a)

00:14.1 IDE interface: ATI Technologies Inc SB700/SB800 IDE Controller

00:14.2 Audio device: ATI Technologies Inc SBx00 Azalia (Intel HDA)

00:14.3 ISA bridge: ATI Technologies Inc SB700/SB800 LPC host controller

00:14.4 PCI bridge: ATI Technologies Inc SBx00 PCI to PCI Bridge

00:14.5 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI2 Controller

00:18.0 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] HyperTransport Configuration

00:18.1 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Address Map

00:18.2 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] DRAM Controller

00:18.3 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Miscellaneous Control

00:18.4 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Link Control

01:00.0 VGA compatible controller: ATI Technologies Inc Radeon HD 3870

01:00.1 Audio device: ATI Technologies Inc Radeon HD 3870 Audio device

02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01)

03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01)

04:02.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306 Fire II IEEE 1394 OHCI Link Layer Controller (rev c0)

```

lsmod:

```

Module                  Size  Used by

msdos                   8008  0 

snd_pcm_oss            34288  0 

snd_mixer_oss          14568  1 snd_pcm_oss

snd_seq_oss            28816  0 

snd_seq_midi_event      7480  1 snd_seq_oss

snd_seq                50128  4 snd_seq_oss,snd_seq_midi_event

snd_seq_device          7388  2 snd_seq_oss,snd_seq

video                  20124  0 

backlight               4944  1 video

output                  3256  1 video

ac                      3752  0 

battery                 7624  0 

button                  7304  0 

fan                     3960  0 

thermal                18808  0 

processor              42656  1 thermal

thermal_sys            11600  4 video,fan,thermal,processor

snd_hda_codec_atihdmi     3736  1 

snd_hda_codec_realtek   243340  1 

snd_hda_intel          25880  0 

snd_hda_codec          63352  3 snd_hda_codec_atihdmi,snd_hda_codec_realtek,snd_hda_intel

snd_pcm                71184  3 snd_pcm_oss,snd_hda_intel,snd_hda_codec

snd_timer              21208  2 snd_seq,snd_pcm

snd                    61544  10 snd_pcm_oss,snd_mixer_oss,snd_seq_oss,snd_seq,snd_seq_device,\

                                         snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_pcm,snd_timer

soundcore               7744  1 snd

snd_page_alloc          9528  2 snd_hda_intel,snd_pcm

r8169                  31884  0 

rtc                     7912  0 

tg3                   102636  0 

libphy                 23192  1 tg3

e1000                 114156  0 

fuse                   53120  0 

jfs                   152896  0 

raid10                 19752  0 

raid456               120872  0 

async_memcpy            2312  1 raid456

async_xor               3800  1 raid456

xor                     5384  2 raid456,async_xor

async_tx                3848  3 raid456,async_memcpy,async_xor

raid1                  20184  0 

raid0                   6360  0 

dm_bbr                 10320  0 

dm_snapshot            17592  0 

dm_mirror              14016  0 

dm_region_hash         12136  1 dm_mirror

dm_log                  9724  2 dm_mirror,dm_region_hash

dm_mod                 56624  4 dm_bbr,dm_snapshot,dm_mirror,dm_log

scsi_wait_scan          1352  0 

sbp2                   22340  0 

ohci1394               29268  0 

ieee1394               86640  2 sbp2,ohci1394

sl811_hcd              10840  0 

usbhid                 24336  0 

ohci_hcd               22180  0 

uhci_hcd               21536  0 

usb_storage           134880  1 

ehci_hcd               33796  0 

usbcore               142576  7 sl811_hcd,usbhid,ohci_hcd,uhci_hcd,usb_storage,ehci_hcd

lpfc                  261844  0 

qla2xxx               204180  0 

megaraid_sas           36092  0 

megaraid_mbox          29432  0 

megaraid_mm             9624  1 megaraid_mbox

megaraid               40392  0 

aacraid                68948  0 

sx8                    15192  0 

DAC960                 66960  0 

cciss                  36584  0 

3w_9xxx                31256  0 

3w_xxxx                23664  0 

mptsas                 33064  0 

scsi_transport_sas     30920  1 mptsas

mptfc                  16640  0 

scsi_transport_fc      43980  3 lpfc,qla2xxx,mptfc

scsi_tgt               13168  1 scsi_transport_fc

mptspi                 17608  0 

mptscsih               32872  3 mptsas,mptfc,mptspi

mptbase                78916  4 mptsas,mptfc,mptspi,mptscsih

atp870u                26928  0 

dc395x                 31364  0 

qla1280               116160  0 

dmx3191d               11144  0 

sym53c8xx              70176  0 

gdth                   79080  0 

advansys               72976  0 

initio                 17512  0 

BusLogic               22928  0 

arcmsr                 22336  0 

aic7xxx               116780  0 

aic79xx               134732  0 

scsi_transport_spi     24024  5 mptspi,dmx3191d,sym53c8xx,aic7xxx,aic79xx

sg                     29216  0 

pdc_adma                7852  0 

sata_inic162x          10172  0 

sata_mv                24996  0 

ata_piix               25628  0 

ahci                   33416  0 

sata_qstor              7916  0 

sata_vsc                6348  0 

sata_uli                5084  0 

sata_sis                6236  0 

sata_sx4               10844  0 

sata_nv                24560  0 

sata_via               11132  0 

sata_svw                6268  0 

sata_sil24             14332  0 

sata_sil               10592  0 

sata_promise           12716  0 

pata_sl82c105           5544  0 

pata_cs5530             6504  0 

pata_cs5520             6440  0 

pata_via               10092  0 

pata_jmicron            3912  0 

pata_marvell            4504  0 

pata_sis               13196  1 sata_sis

pata_netcell            3836  0 

pata_sc1200             4648  0 

pata_pdc202xx_old       6392  0 

pata_triflex            4956  0 

pata_atiixp             5592  0 

pata_opti               4684  0 

pata_amd               13372  0 

pata_ali               11928  0 

pata_it8213             5452  0 

pata_pcmcia            14120  0 

pcmcia                 35200  1 pata_pcmcia

firmware_class          8520  3 tg3,qla2xxx,pcmcia

pcmcia_core            36276  1 pcmcia

pata_ns87415            5132  0 

pata_ns87410            4760  0 

pata_serverworks        7880  0 

pata_artop              6892  0 

pata_it821x            11836  0 

pata_optidma            6832  0 

pata_hpt3x2n            6744  0 

pata_hpt3x3             5340  0 

pata_hpt37x            13752  0 

pata_hpt366             7144  0 

pata_cmd64x             7768  0 

pata_efar               5372  0 

pata_rz1000             4444  0 

pata_sil680             7004  0 

pata_radisys            4892  0 

pata_pdc2027x           8860  0 

pata_mpiix              5004  0 

libata                173004  50 pdc_adma,sata_inic162x,sata_mv,ata_piix,ahci,sata_qstor,sata_vsc,sata_uli,sata_sis,sata_sx4,\

                                         sata_nv,sata_via,sata_svw,sata_sil24,sata_sil,sata_promise,pata_sl82c105,\

                                         pata_cs5530,pata_cs5520,pata_via,pata_jmicron,pata_marvell,pata_sis,pata_netcell,pata_sc1200,\

                                         pata_pdc202xx_old,pata_triflex,pata_atiixp,pata_opti,pata_amd,pata_ali,pata_it8213,\

                                         pata_pcmcia,pata_ns87415,pata_ns87410,pata_serverworks,pata_artop,pata_it821x,pata_optidma,\

                                         pata_hpt3x2n,pata_hpt3x3,pata_hpt37x,pata_hpt366,pata_cmd64x,pata_efar,\

                                         pata_rz1000,pata_sil680,pata_radisys,pata_pdc2027x,pata_mpiix

```

Line breaks added by NeddySeagoon to preserve thread formatting

----------

## cyrillic

 *SeaHag wrote:*   

> lspci:
> 
> ```
> 
> 00:11.0 RAID bus controller: ATI Technologies Inc SB700/SB800 SATA Controller [RAID5 mode]
> ...

 

This is most likely not a RAID controller, just a SATA controller.

The easy way to confirm this is to see if the drives are listed individually when you do this.

```
# fdisk -l 
```

----------

## SeaHag

Yes, they appear as sda and sdb. These are two 750G drives that I put into a RAID0 in the BIOS. It should be a 1.5TB raid array. Do I need to load any modules or something like that. I'm new to Gentoo, this is my first installation. In Windows you have to load a floppy with drivers that used to be called "F6 floppy" before it will see the RAID and install on it. Is there something similar I need to do here? I wonder why there are no partitions on the sdb? I set SATA mode to RAID in the BIOS then go into a config ROM on boot to setup the RAID. I setup the raid once and installed Windows on it. Now trying to put Gentoo on another partition.

```

Disk /dev/sda: 750.1 GB, 750156374016 bytes

255 heads, 63 sectors/track, 91201 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Disk identifier: 0xd187e9b9

   Device Boot      Start         End      Blocks   Id  System

/dev/sda1   *           1          13      102400    7  HPFS/NTFS

Partition 1 does not end on cylinder boundary.

/dev/sda2              13       13055   104754176    7  HPFS/NTFS

/dev/sda3           13055       26109   104857600    6  FAT16

/dev/sda4           26109      182365  1255127040    f  W95 Ext'd (LBA)

/dev/sda5   ?      127555      201457   593616790+   e  W95 FAT16 (LBA)

Disk /dev/sdb: 750.1 GB, 750156374016 bytes

255 heads, 63 sectors/track, 91201 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Disk identifier: 0x00000000

```

----------

## Cyker

I think you need to use something called dmraid to support 'fakeraid' systems like the ones built in to motherboards; I don't know much more than that 'tho as I've never tried it!

----------

## SeaHag

There's somthing very fishy going on here. Does that fdisk output look alright to you? When I create the raid0 array the partitions are all on one drive and the sizes look larger than the actuall disc. Am I not reading it correctly? These are 750G drives but it looks like the partition size for /dev/sda4 is over 1TB. The partitions for the raid0 should be across both discs.

----------

## Monkeh

 *SeaHag wrote:*   

> There's somthing very fishy going on here. Does that fdisk output look alright to you? When I create the raid0 array the partitions are all on one drive and the sizes look larger than the actuall disc. Am I not reading it correctly? These are 750G drives but it looks like the partition size for /dev/sda4 is over 1TB. The partitions for the raid0 should be across both discs.

 

When dealing with fakeraid there's no such thing as logic.  :Wink: 

----------

## energyman76b

do the sane thing. Forget mainboard fakeraid.

Set the sata controller in bios in ahci mode, setup md software raid and live a happy life without problems.

----------

## NeddySeagoon

SeaHag,

Thats correct. When you set up a fakeraid raid0 array, the controller writes the partition table on one drive and stripes the drives so the OS sees it as one volume bigger than the individual drives. Your are not supposed to look at the fakeraid volume parts that reside on its component drives.

Keep in mind that the BIOS and dmraid hide the physical underlying drives.

----------

## hielvc

Edit: This is in-correct see Neddy's 2 post below ===> SeaHag Is this a dual boot box, you are running windows and linux? If so ypu need to use dmraid. Windows, unless you  ae  using wine doesnt,  understand  linux software raid.

----------

## NeddySeagoon

hielvc,

Both Windows and Linux understand Vistas 'virtual disks' which is another varient of software raid.

----------

## Sysa

 *hielvc wrote:*   

> SeaHag Is this a dual boot box, you are running windows and linux? If so ypu need to use dmraid. Windows, unless you  ae  using wine doesnt,  understand  linux software raid.

 

You can (should to?) use different partitions for Linux (RAID) and Windows:

e.g. 

sda1 - Windows disk C: or RAID disk1

sdb1 - Windows disk D: or RAID disk2

sda2 - Linux RAID (disk1)

sdb2 - Linux RAID (disk2)

...

etc

----------

## NeddySeagoon

Sysa,

The problem is that windows uses fakeraid to raid whole drives and linux normally donates partitions to a raid set.

When you set up a windows raid0 set, the kernel canot see inside it. You must use dmraid.

----------

## hielvc

Thanks for the correction Neddy.

----------

## SeaHag

Thanks for replys. sorry I took so long to get back, I've been resetting everything up on single drives. During my adventures I learned what "fakeraid" is. CRAP!

 *Quote:*   

> 
> 
> When dealing with fakeraid there's no such thing as logic.
> 
> 

 

No kidding, what a big marketting scam that wasted a bunch of my time. I thought that since it was onboard that it was hardware raid. I thought they just took the same electronics that were on an addin hba and put it on the motherboard like they did with sound and network. I was duped like many others.

 *Quote:*   

> 
> 
> Set the sata controller in bios in ahci mode, setup md software raid and live a happy life without problems.
> 
> 

 

yup, live and learn. 

 *Quote:*   

> 
> 
> When you set up a fakeraid raid0 array, the controller writes the partition table on one drive and stripes the drives so the OS sees it as one volume bigger than the individual drives. 
> 
> 

 

Stripes the drives? What do you mean? With no partition on sdb? Note how you said the controller writes the partition table not windows. And why create a partition table onl;y on one drive? If I create a raid0 in the bios then go to install linux with no windows at all can linux see the fake raid. I think yes, I read something about modprobe raid0 at install and dmraid etc. but if it's not a real raid0 across both drives then forget it. In raid0 there should be equal partitions on all drives in the array. 

 *Quote:*   

> 
> 
> Your are not supposed to look at the fakeraid volume parts that reside on its component drives.
> 
> 

 

Why not? I need to know how much space is left to create other partitions for my linux raids. I've seen many raid0s in my life and you should always be able to see the partitions. Otherwise how do you know if they're created correctly or how big they are? You should be able to create partitions on a raid and see them.

 *Quote:*   

> 
> 
> SeaHag Is this a dual boot box, you are running windows and linux? If so ypu need to use dmraid. Windows, unless you ae using wine doesnt, understand linux software raid.
> 
> 

 

Yes dual booting windows and linux. I don't care about windows seeing linux raid or vice versa. I just want to install both on a raid0 for speed. So if I use dmraid I need to create partitions. If fdisk says there's a 1TB partition on a 750G drive then how much space do I have left to make partitions for dmraid?

 *Quote:*   

> 
> 
> You can (should to?) use different partitions for Linux (RAID) and Windows: 
> 
> e.g. 
> ...

 

Yes that's what I thought this stupid piece of junk would do but nooo. I thought that if I said make a raid0 it would create two equal partitions on each drive (2 drive raid 0) but nooo, It has to be some retarded, bastardized piece of marketing turd.

 *Quote:*   

> 
> 
> The problem is that windows uses fakeraid to raid whole drives and linux normally donates partitions to a raid set.
> 
> 

 

Windows or the controller? I'm still not clear who is writing this partition table and how you can put bigger partitions than the size of the actual drive. Are these just bogus numbers to fool the system or something? Then is it realy writing back and forth to two drives or just one? In raid0 it should be writing to both drives. If it's not they're blatantly lying to us. If they are then there must be some partition to write to and so you can see how much space is left on the drive to make more partitions. I don't see any partitions on my /dev/sdb so I should be able to use it all. Are you saying that it makes some kind of partition type that linux fdisk can't see?

 *Quote:*   

> 
> 
> When you set up a windows raid0 set, the kernel canot see inside it. You must use dmraid.
> 
> 

 

I don't care about windows seeing linux raid or vice versa. All I wanted was a real raid0. RAID0 is supposed to be equal partitions on each drive and if it's not then what the hell is this stupid thing? This makes no sense. I've come to the conclusion that it's bull and not worth it and not what I expected.Last edited by SeaHag on Fri Jul 17, 2009 1:33 am; edited 2 times in total

----------

## krinn

 *SeaHag wrote:*   

> 
> 
>  *Quote:*   
> 
> When you set up a fakeraid raid0 array, the controller writes the partition table on one drive and stripes the drives so the OS sees it as one volume bigger than the individual drives. 
> ...

 

He means your bios for a raid0 (called stripping) add both drives capacity into 1 big drive, so 2x200g will be seen as 1x400g, and in real raid, the controller will write in 1 drive then in the other drive, so as both drives are working, you get speed increase.

With fake raid, the bios add the 2 drives to build 1 big drive, but your cpu (software) is in charge of balancing the write request to the both disks = no difference with software raid in performance so.

as info, raid1 is called mirroring, it's taking 1 drive and copy exact same content to the 2nd one, so you take 2x200g and end with 1x200g but you have the same copy on the 2nd drive. There's plenty other raid type.

----------

## SeaHag

..."the controller will write in 1 drive then in the other drive..."

How with no partition in the second drive? My fdisk output above shows no partition on /dev/sdb. This is a raid0 made of two 750G drives, /dev/sda and /dev/sdb. Raid0 should have equal partitions on each drive.

----------

## krinn

no, the /dev/sda and /dev/sdb will be use to create a big /dev/md0 and that /dev/md0 will need to get its partition.

edit: if it help you better: with 1 partition you could write to a full disk, right? You don't need 2 partitions in 1 disk to write 1-50% of the disk and another one to write 51-100% on that disk.

It's the same for stripping, consider half your disk is 100% of /dev/sda and the other half of it is the /dev/sdb, and to write on them 1 partition is all you need.Last edited by krinn on Fri Jul 17, 2009 1:48 am; edited 1 time in total

----------

## energyman76b

usually when the controller sets up the 'raid' it cares about everything - so you might not see the partitions - but the controller does.

Another reason why fakeraid is problematic - if you try to switch from say nvidia fakeraid to intel or amd fakeraid you probably won't be able to access your data.

Go software route. And Raid5 or 6.

----------

## energyman76b

 *krinn wrote:*   

> no, the /dev/sda and /dev/sdb will be use to create a big /dev/md0 and that /dev/md0 will need to get its partition.
> 
> edit: if it help you better: with 1 partition you could write to a full disk, right? You don't need 2 partitions in 1 disk to write 1-50% of the disk and another one to write 51-100% on that disk.
> 
> It's the same for stripping, consider half your disk is 100% of /dev/sda and the other half of it is the /dev/sdb, and to write on them 1 partition is all you need.

 

when you use md raid (software raid) you don't raid disks but partitions...

----------

## krinn

 *energyman76b wrote:*   

> 
> 
> when you use md raid (software raid) you don't raid disks but partitions...

 

If you wish to harder it, you'll lost him again...

----------

## SeaHag

 *Quote:*   

> 
> 
> no, the /dev/sda and /dev/sdb will be use to create a big /dev/md0 and that /dev/md0 will need to get its partition.
> 
> 

 

You lost me there. Used to create big /dev/md0 by who? Who is creating md0? Windows doesn't know anything about mds right? I created a raid0 in the fakeraid ROM then made a 100G partition on it during the windows installation and installed windows. Then made another 100G primary partition and 500G data partition in the 1.2TB extended partition in windows, no linux involved yet. Then booted on the gentoo install CD to make more partitions for Gentoo that I though would go onto both drives till I saw the fdisk output. If I create a 100G partition in windows there should be a 50G partition on each drive. Here's my Gentoo fdisk -l output again after booting on the install CD but before installing any Gentoo with comments I added after each line. No linux installed yet. Why is there partitions on /dev/sda and not on /dev/sdb? If you're going to stripe back and forth between both drives don't you need partitions on both drives? The total of partitions on /dev/sda is around 1.5TB, the size of the raid0 of both 750G drives. That doesn't make any sense. If I want to use linux software raid how much space do I have on /dev/sda to make partitions? Windows is supposed to be striping back and forth to both drives but now I'm wondering if it really is.

```

Disk /dev/sda: 750.1 GB, 750156374016 bytes 

255 heads, 63 sectors/track, 91201 cylinders 

Units = cylinders of 16065 * 512 = 8225280 bytes 

Disk identifier: 0xd187e9b9 

   Device Boot      Start         End      Blocks   Id  System 

/dev/sda1   *           1          13      102400    7  HPFS/NTFS                  #100MB Windows 7 boot partition

Partition 1 does not end on cylinder boundary.  

/dev/sda2              13       13055   104754176   7  HPFS/NTFS                #100G Windows 7 system partition 

/dev/sda3           13055       26109   104857600    6  FAT16                   #100G unused partition

/dev/sda4           26109      182365  1255127040    f  W95 Ext'd (LBA)      #the 4th extended partition 1.2TB !?!

/dev/sda5   ?      127555      201457   593616790+   e  W95 FAT16 (LBA)      #500G data partition in the extended partition. Appears as ntfs in windows.

Disk /dev/sdb: 750.1 GB, 750156374016 bytes 

255 heads, 63 sectors/track, 91201 cylinders 

Units = cylinders of 16065 * 512 = 8225280 bytes 

Disk identifier: 0x00000000

```

 *Quote:*   

> 
> 
> Go software route. And Raid5 or 6.
> 
> 

 

I don't want raid 5 or 6 that takes at least 3 or 4 drives for the later. That's too much heat in the PC case then you need all these fans that can fail blah blah blah and raid 5 is slower cuz it needs to calulate XOR and also suffers write penalty. It also looses one disks worth of space for the parity data (raid5, raid6 looses two disk worth right?). A 3 drive raid0 will kick ass on a 3 drive raid5 and have 50% more space. I don't care about data safety, I have anything important well backed up. I just wanted a faster system but it's not worth the headaches. I was fooled by marketing that it was a true hardware raid since it was onboard.

 *Quote:*   

> 
> 
> when you use md raid (software raid) you don't raid disks but partitions...
> 
> 

 

Right, and a raid0 should have equal size partitions on each disk.

 *Quote:*   

> 
> 
> If you wish to harder it, you'll lost him again...
> 
> 

 

lol

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## energyman76b

so  three disk raid is too hot, but disk raid0 is not?

you know that the xoring is something that doesn't even create any measurable load on modern cpu's? 

but ok - everything is backed up. You just suffer from the 'reinstall everything' when a disk dies. If you can live with that, great.

About 'fooled by vendors' - well at least the linux side was always very vocal about it - especially the fact that linux software raid beats fakeraid on performance almost always.

Now, I am lost a bit: what do you plan to do now?

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## SeaHag

 *Quote:*   

> 
> 
> so three disk raid is too hot, but disk raid0 is not?
> 
> 

 

Yes, you are correct  equal number of drives qives equal heat but I only want a 2 drive raid0 not 3 or 4 drive raid5 or 6. What I usually would do is something like take 2 500G drives in a raid0 for 1TB of space then back it up on a 1TB single drive. So for 3 drives I get 2TB of space plus 2 drive raid0 for speed. I could also set those same 3 drives up as a 3 drive raid5 which would be 3 times the smallest drive which would be 1.5TB of space minus 500G for parity would leave me with only 1TB of space plus maybe slower than the 2 drive raid0 for writes because it stripes two drives then calculates parity and writes it to the third drive and also this would waste 500G of the 1TB drive. It may be faster for reads though and I was considering doing that until I started looking into fakeraid and all the problems it causes. And one more thing, I could tolerate loosing two drives in the raid0 and still have a copy of my data. The raid 5 couldn't loose two drives but that would be highly unlikely.

 *Quote:*   

> 
> 
> you know that the xoring is something that doesn't even create any measurable load on modern cpu's?
> 
> 

 

But still slower than raid0 right? not to mention less space. Raid5 and 6 has it's place just not what I want. 

 *Quote:*   

> 
> 
> You just suffer from the 'reinstall everything' when a disk dies. If you can live with that, great.
> 
> 

 

Ever heard of norton ghost or dump/restore? I can ghost my windows partition back in about 7 minutes but it takes about 1.5 hours for 250G worth of data. But I don't mind, I'll just do something else while it's running. And that's another problem with fakeraid, ghost doesn't always see it. 

 *Quote:*   

> 
> 
> About 'fooled by vendors' - well at least the linux side was always very vocal about it - especially the fact that linux software raid beats fakeraid on performance almost always.
> 
> 

 

I still don't even know what fake raid is or how it works? I know it's software raid and no faster so it's not worth the hassle. I'm trying to multi-boot with windows, freebsd, gentoo, and however more linux OSes I can fit. But the FreeBSD install CD keeps rebooting the system if I set it to RAID in the BIOS. It won't even install and if I want to create mds in linux how much space do I have for partitions when it tells me I have 1.5TB worth of partitions on a 750G drive?

 *Quote:*   

> 
> 
> Now, I am lost a bit: what do you plan to do now?
> 
> 

 

lol, disable RAID in the BIOS and use single drives.  :Wink: Last edited by SeaHag on Sat Jul 18, 2009 3:14 am; edited 5 times in total

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## energyman76b

 *SeaHag wrote:*   

>  *Quote:*   
> 
> so three disk raid is too hot, but disk raid0 is not?
> 
>  
> ...

 

raid5 is basically raid0+checksum. So, not necessarily slower.

 *Quote:*   

> 
> 
>  *Quote:*   
> 
> You just suffer from the 'reinstall everything' when a disk dies. If you can live with that, great.
> ...

 

yes, I heard of 'ghost'. Another single point of failure.

 *Quote:*   

> 
> 
>  *Quote:*   
> 
> About 'fooled by vendors' - well at least the linux side was always very vocal about it - especially the fact that linux software raid beats fakeraid on performance almost always.
> ...

 

----------

## SeaHag

 *Quote:*   

> 
> 
> you know that the xoring is something that doesn't even create any measurable load on modern cpu's?
> 
> 

 

It's not so much the calculation of the parity but writing it to disk that slows it down. That's one extra wrtie operation that the raid0 doesn't have to do.

 *Quote:*   

> 
> 
> raid5 is basically raid0+checksum. So, not necessarily slower.
> 
> 

 

Ya it is, do some benchmark tests, it writes the stripe on the first two drives, calulates the XOR of the data then writes that on the third drive. That's three writes instead of two. Still more work than just writing the stripe only. So it will be slower on writes, reads should be the same. I'm talking about 2 drive raid0 vs. 3 drive raid5 not 3 vs. 3 although it doesn't really matter, 3 drive raid0 will be even faster than 2. And if raid5 has to write a partial stripe it must first read it up into a buffer, modify the buffer with the new data, calculate the XOR then write that stripe back down. That's the write penalty. I did some benchmark tests at work and raid5 was the slowest of raid0, 1, and 10. I was going to try raid5 but BSD wouldn't install with raid enabled and the fdisk output looked all screwy and ghost might have trouble with it and it just snowballed and got worse. I thought it was real hardware raid and if it was it would have been great. But I learned my lesson and wasted a couple of weeks.

----------

