RAID, an acronym for Redundant Array of Independent Disks (sometimes incorrectly referred to as Redundant Array of Inexpensive Disks), is a technology that provides increased storage functions and reliability through redundancy. -Wikipedia

learn more… | top users | synonyms

10
votes
12answers
2k views

How to remember RAID levels? [duplicate]

How do you remember(if you really do :-)) all the different levels and what each level does? Can anyone suggest an easy way to remember?
10
votes
7answers
712 views

Can a RAID 4 disk setup crash if only 1 hard disk fails? [closed]

I am a web developer. I have not much experience in hardware. For this reason, I use managed servers. This morning, one of the drives in our setup failed. However, the full site went down. I ...
10
votes
7answers
35k views

What is a (raid-controller-) BBU for?

I am wondering what's the purpose of a BBU. My first understanding was, that it enables the cache to write the data to the disc during a power failure. But some specifications say that a BBU can hold ...
10
votes
1answer
18k views

How exactly does a SAS SFF-8087 breakout cable work? + RAID/connection questions

Please let me know if my question does not makes any sense as I am not sure if I am interpreting it correctly from my thoughts due to my lack of technical knowledge on this. If I am using a ...
10
votes
3answers
10k views

Battery Backed Write Cache

I recently got some U server price quotes and some of them include BBWC: What exactly does it do? Is it just for RAID configurations? If there is a power malfunction, isn't the data loss ...
10
votes
3answers
18k views

Can we mount multiple disks as one directory?

Are there way to mount the different disks as one directory? Assuming I have some disks with ext4 partitions: /dev/sda1 1Tb mounted as /store1 /dev/sda2 2Tb mounted as /store2 /dev/sdb1 2Tb mounted ...
10
votes
2answers
1k views

Are consumer class hard disks okay for zfs?

I just recently bought a new server an HP DL380 G6. I replaced the stock smart array p410 controller with an LSI 9211-8i. My plan is use ZFS as the underlying storage for XEN which will run on the ...
10
votes
2answers
1k views

Why is my RAID1 read access slower than write access?

I have done some simple performance tests and it seems that reading from my RAID1 is slower than writing: root@dss0:~# for i in 1 2 3; do dd if=/dev/zero of=/dev/sda bs=1048576 count=131072; done ...
10
votes
7answers
4k views

Hot spare or extra parity drive in RAID array?

In a different question about configuring a RAID array, the author is building a RAID array with 8 drives. One answer suggests using 7 drives in RAID 5 with one left over as a hot spare. Since RAID 6 ...
10
votes
8answers
31k views

Guidelines for the maximum number of disks in a RAID set?

In any of the RAID levels that use striping, increasing the number of physical disks usually increases performance, but also increase the chance of any one disk in the set failing. I have this idea ...
10
votes
3answers
14k views

How do I rename an mdadm raid array?

I have assembled a new raid array to replace an old one. However, this new array got assigned an automatic name of /dev/md127 and I want to rename it to /dev/md3, so that I don't have to change ...
10
votes
5answers
14k views

How do you monitor the health of a mirrored disk in Windows?

I have a Mirrored Dynamic disk on my Windows 2003 Server. How do you monitor the health of the volume? Is there a way to have the server send an email when there is an issue with the volume? Is there ...
10
votes
1answer
7k views

Easy to expand Linux software RAID 5 with XFS. Best practices?

I use my Ubuntu machine as a file server for Windows/Linux/Mac clients using a Samba share. I need it to be easily expandable by just adding more hard drives without having to move any data back and ...
10
votes
2answers
1k views

Areca 1280ml RAID6 volume set failed

Today we hit some kind of worst case scenario and are open to any kind of good ideas. Here is our problem: We are using several dedicated storage servers to host our virtual machines. Before I ...
9
votes
2answers
7k views

How to upgrade a ZFS RAID-Z array to larger disks on OpenSolaris?

I'm planning on installing OpenSolaris on my home server (right now it has Linux) and I would like to know how to prepare for upgrading the server to have larger hard drives in the future. Now the ...
9
votes
3answers
9k views

Is a large RAID-Z array just as bad as a large RAID-5 array?

For a long time I've heard about how bad an idea a large (>5TB?) RAID-5 array is simply because there's a high risk for another drive to fail. Has RAID-Z1 managed to remedy this for an array of any ...
9
votes
3answers
8k views

explain md's raid10,f2

I know how most of the various RAID's work. But I stumbled on the recommended raid10,f2 mode while researching linux software raid. I don't really understand how it works on 2 or 3 disks. could ...
9
votes
2answers
35k views

What is the fastest and safest RAID combination for SATA drives?

I wonder what is the fastest and safest RAID combination for SATA drives and general use (some write, mostly read)? RAID 0 is fast but utterly unsafe, RAID 1 is safe but slow, RAID 5 is safe but not ...
9
votes
6answers
8k views

ZFS Like Alternatives on Windows

Conceptually, and I don't think I am alone here, I love the concepts of ZFS. You can create one big disk, everything is stored on multiple drives, and you can grow and shrink the pool and drive at ...
9
votes
4answers
956 views

Do disks in Raid-1 function outside of the raid?

Raid-1 is mirroring two disks (if I haven't messed up completely here :p). Does that mean that I could take one disk out and put it into another machine and it would work like a normal disk? Or does ...
9
votes
3answers
1k views

Best practice for 24 Disk Array

we have just migrated for our old fibre SAN storage to an IBM v3700 storwize with 24 SAS 600GB disks. This storage is connected directly to two IBM ESXi 5.5 servers each with two 6Gbps multipath SAS ...
9
votes
5answers
5k views

Squid or Other HTTP Caches with SSD Cache Store?

I'm contemplating setting up a squid (or possibly varnish) cache on a system with SSD drives. The obvious benefit is that these systems have great READ speeds and I expect my hit ratios to be fairly ...
9
votes
1answer
998 views

Why does df shows only half the size of a RAID10 array?

I've created a RAID10 array using 4 75G drives, to create a storage of 150G. After everything finished (including the initial syncing), everything looked good except the output of df -h which showed ...
9
votes
2answers
1k views

How to check CentOS 6 Server VM Host after a power falure?

This afternoon, someone at our office decided to pull the plug out of our server because it was storming outside. They didn't shut it down, they just pulled the plug out while it was running. The ...
8
votes
3answers
2k views

Linux fileserver storage pool

Is it possible to get linux server to share several hard drives as one storage pool through Samba? So that when I use the share I don't have to worry about saving to a certain drive that has free ...
8
votes
3answers
1k views

Is it safe to write data to a RAID 6 while it's rebuilding?

I have a test RAID controller on my network which hosts a very large RAID 6 (11 drives, 3TB each). One of the drives failed, and the array is now rebuilding. At this rate, I think it will take about 3 ...
8
votes
4answers
22k views

Why do I need a raid battery pack?

I'm trying to understand why one would add a batterypack to a raid card. It seems to me like if power goes down, running just the raid card is going to do little good: without power for HDs and ...
8
votes
2answers
5k views

Can different drive speeds and sizes be used in a hardware RAID configuration w/o affecting performance?

Specifically, I have a RAID 1 array configuration with two 500gb 7200rpm SATA drives mirrored as logical drive 1 (a) and two of the same mirrored as logical drive 2 (b). I'd like to add two 1tb ...
8
votes
4answers
4k views

One large RAID 10 vs several smaller arrays?

My question is: when is it appropriate to simply create one large array with fast read & write performance, such as RAID 10, instead of creating smaller arrays for specific applications? It ...
8
votes
3answers
1k views

Migrate raw disk image over LAN

Here is my situation: Two dedicated servers in the same datacenter with gigabit ethernet between them. Both dedicated servers booted into a rescue environment based on Debian Squeeze with extra ...
8
votes
2answers
15k views

Megacli is killing me, any help appreciated

I run a server with 2 drives in raid0 configured through BIOS. I just added 2 more drives using hotplug (the server is dell r610 with RHEL 5.4 64bit) and I would like to configure a separate raid0 ...
8
votes
4answers
104k views

How to check if hardware RAID is configured?

I have several servers running Windows 2008 and Red Hat 5 that are capable of hardware RAID. How do I check that hardware RAID is configured?
8
votes
1answer
5k views

mdadm and 4k sectors (advanced format)

There are numerous questions on Serverfault about aligning 4k sectors disks, but one thing is not really clear to me yet. I successfully aligned my RAID1+LVM. One of the things I did was use mdadm ...
8
votes
8answers
15k views

How to Monitor an Adaptec/Intel ICH10R RAID Controller (any SNMP notification options?)

SuperMicro's Super Doctor III is the software I was looking for. It is SuperMicro's equivalent of IBM's ServerGuide or Dell's OpenManage. Unfortunately, while it supports hardware monitoring and SNMP ...
8
votes
3answers
2k views

Restoring an Amazon EBS RAID0 array from snapshots taken with ec2-consistent-snapshot

I've configured a new MySQL server on Amazon EC2 and decided to store my data on a EBS RAID0 Array. So far so good, and I've tested taking snapshots of those devices with ec2-consistent-snapshot, ...
8
votes
1answer
12k views

Ubuntu server, gpt partition table, mdadm, grub boot fail

Basic working system details: I used the Ubuntu 12.04 server CD to install a server. I have 4 disks. On all disks I did the following, similar to this howto : created a 2GB swap partition created ...
8
votes
2answers
964 views

Linux RAID-0 performance doesn't scale up over 1 GB/s

I have trouble getting the max throughput out of my setup. The hardware is as follow : dual Quad-Core AMD Opteron(tm) Processor 2376 16 GB DDR2 ECC RAM dual Adaptec 52245 RAID controllers 48 1 TB ...
8
votes
2answers
1k views

How to attach an existing RAID1 to a fresh Linux system?

I have a RAID1 currently operating on a single hard drive (yes, the mirror is absent). Is it possible to reorganize my system using the following algorithm? I set up another single-disk RAID1 (onto ...
8
votes
3answers
11k views

How to resize RAID1 array with mdadm?

I've running Ubuntu 11.04 (kernel 2.6.38-11). I replaced 2x160GB with 2x500GB drives. They are configured as RAID1. The partition tables show the right sizes. Here's sfdisk: # sfdisk -d /dev/sdb # ...
8
votes
1answer
2k views

Can I use dmraid instead of md (mdadm) to make software RAID-1 and RAID-1+0 volumes?

On a related question about SSDs and TRIM (see: Possible to get SSD TRIM (discard) working on ext4 + LVM + software RAID in Linux? ), it turns out that dmraid may now (or shortly) support TRIM on ...
8
votes
2answers
1k views

Linux Software Raid 10 hung after 1 drive failed, mdadm will not let me force remove the faulty device

I have a Linux software raid 10 setup consisting of 5 RAID 1s (Two drives per mirrored setup) and a RAID 0 across all 5 RAID 1 pairs. To test that none of the drives were going to fail quickly under ...
7
votes
7answers
9k views

Can I just remove a disk from a live RAID 1 array?

I've read the story about the manager taking out a disk from a RAID 5 array, and then a second one, but I’d just like to try out for myself what happens when I simply disconnect a disk from a live ...
7
votes
4answers
4k views

RAID 1+0 vs RAID 0+1

I went with some advice I was given from someone I know to go with a RAID setup for this server I ordered. The specs are below. I plan on using this server to host multiple sites in a PHP/MySQL ...
7
votes
3answers
36k views

How to monitor the hard disk status behind Dell PERC H710 Raid Controller with CentOS 6?

I have a Dell server running CentOS 6 using PERC H710 Raid Controller card with Raid 5 setup and I want to monitor the hard disk failure/working status behind the Raid Controller. Then I should be ...
7
votes
2answers
2k views

Large RAID stripe size wastes space with small files?

I'm planning a Maildir storage with RAID 0+1(or RAID 10, RAID 5) on XFS filesystem and XFS will be created with stripe unit and width that RAID will use. I don't determine RAID stripe size yet, but ...
7
votes
5answers
26k views

Disabling RAID feature on HP Smart Array P400

I'm planning to use ZFS on my system (HP ML370 G5, Smart Array P400, 8 SAS disk). I want ZFS to manage all disks individually, so it can utilize better scheduling (i.e. I want to use software RAID ...
7
votes
3answers
2k views

Do I need a second RAID controller for fault-tolerance?

I have a server with 3 hard drives installed, and a total capacity of 6. We're planning to max it out, but our consultant also suggested getting a second RAID controller "for redundancy" to support ...
7
votes
8answers
748 views

Recommendations for hardware RAID controllers [closed]

I'm looking for a hardware RAID controller. I want something that: Can support 8 or maybe 16 hard drives Won't randomly break, lose my data, etc. Does anyone have recommendations? It seems like ...
7
votes
3answers
736 views

RAID array Considerations - Any advice?

We just bought a Dell PowerEdge r510 (12 drive bays) that will fill the role of an archive server. We have 6 drives (1TB each) installed. The plan is to have all the drives in a single RAID array and ...
7
votes
5answers
11k views

Poor read performance on Dell Perc H200 RAID10 with (4) 1TB 7200rpm 64MB drives

I am seeing only 50MB/s reads: ensnare@box:~$ sudo hdparm -tT /dev/sda [sudo] password for ensnare: /dev/sda: Timing cached reads: 4592 MB in 2.00 seconds = 2296.48 MB/sec Timing buffered disk ...