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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