[CentOS] raid 5 install

Fri Jun 28 21:19:45 UTC 2019
Rob Kampen <rkampen at kampensonline.com>

On 29/06/19 2:46 AM, Blake Hudson wrote:
> Nikos Gatsis - Qbit wrote on 6/27/2019 8:36 AM:
>> Hello list.
>> The next days we are going to install Centos 7 on a new server, with 
>> 4*3Tb sata hdd as raid-5. We will use the graphical interface to 
>> install and set up raid.
>> Do I have to consider anything before installation, because the disks 
>> are very large?
>> Does the graphical use the parted to set/format the raid?
> Hi Nikos, I've read the other posts in this thread and wanted to 
> provide my perspective. I've used Linux RAID at various times over the 
> past 10-20 years with both desktop and server class hardware. I've 
> also used hardware RAID controllers from 3ware, Adaptec, LSI, AMI, and 
> others with IDE, SATA, SAS, and SCSI drives. The goal of RAID 1 and 
> above is to increase availability. Unfortunately, I've never had Linux 
> software RAID improve availability - it has only decreased 
> availability for me. This has been due to a combination of hardware 
> and software issues that are are generally handled well by HW RAID 
> controllers, but are often handled poorly or unpredictably by desktop 
> oriented hardware and Linux software.
Sorry for your poor experience. I have used and achieved much improved 
availability by using Linux Software RAID - most often I use RAID 1 and 
had disks fail with no impact to the client other than slightly reduced 
response times (in fact they were totally unaware that a drive had 
failed, until I told them). Replaced the faulty drive (done by a local 
person who barely knew how to use a screw driver), resynchronized and 
all is well - zero data lost. It was a hot swap bay and thus the server 
did not even have to be powered down - zero customer noticed impact - 
100% availability.

> Given that Linux software RAID does not achieve the goal of RAID 
> (improved availability), my recommendation would be to avoid it. If 
> you are looking for a backup mechanism, RAID is not it (use a backup 
> program instead). If you do need high availability, my recommendation 
> is to purchase an LSI based RAID controller. If you plan to use RAID 
> 5, make sure the model you choose has a write cache (this could double 
> the cost of the controller). Used IBM, HP, or Dell RAID controllers 
> are available for a reasonable price or you can purchase a new one 
> from Newegg or wherever. SAS RAID controllers will work with either 
> SAS or SATA drives and you can purchase the appropriate breakout 
> cables for connecting the controller to individual drives. Since 
> you're planning on using 3TB+ drives that are likely 4k native sector, 
> I'd recommend a newer model controller like the Dell PERC H730 (LSI 
> MegaRAID SAS 9361-8i) for RAID5/6 or a PERC H330 (LSI MegaRAID SAS 
> 9341-8i) for RAID 0/1/10.
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