A 10-20$ "hardware" RAID card is nothing more than a opaque, binary driver blob running a crap software-only RAID implementation. Stay well away from it.
A 200$ RAID card offer proper hardware support (ie: a RoC running another opaque, binary blob which is better and does not run on the main host CPU). I suggest to stay away from these cards also because, ...
You have a double disk failure. This means your data is gone, and you will have to restore from a backup. This is why we aren't supposed to use raid 5 on large disks. You want to set up your raid so you always have the ability to withstand two disk failures, especially with large slow disks.
Your options are:
Restoring from backups.
You do have backups, don't you? RAID is not a backup.
Professional data recovery
It's possible, though very expensive and not guaranteed, that a professional recovery service will be able to recover your data.
Accepting your data loss and learning from the experience.
As noted in the comments, large SATA disks ...
You actually part answered this in your question.
The lowest form of RAID is RAID 1. RAID 0 was added well after RAID was defined (can't find reference to a date for this though)
The 0 in RAID 0 is used to signify that actually it isn't considered redundant. Think of it as more True/False where 0 is False.
Sure. I've had battery-backed cache (BBWC) and later flash-backed write cache (FBWC) protect in-flight data following crashes and sudden power loss.
On HP ProLiant servers, the typical message is:
POST Error: 1792-Drive Array Reports Valid Data Found in Array Accelerator
Which means, "Hey, there's data in the write cache that survived the reboot/power-...
Generally I'm pretty sure the answer is no (in fact I know of no controller that does this).
Doing such a synchronization would be incredibly difficult - vibration, temperature, natural power supply fluctuation, etc. all have small effects on the platter rotational speed (and if you want to be REALLY picky, the size of a sector).
You would need to ...
S.M.A.R.T. is not the final word in disk or storage monitoring!! It's a component, but modern RAID controllers use it along with other methods to determine drive and array health.
I'm assuming this is a PERC controller in a Dell PowerEdge server.
The normal Linux-friendly approach to health monitoring of Dell hardware is to install the Dell OMSA agents for ...
You can see the SMART status of the disks with the smartctl command and it's -d argument. For example, to see the first disk in the array:
# smartctl -a /dev/sda -d sat+megaraid,00
smartctl 5.43 2012-06-30 r3573 [x86_64-linux-2.6.32-358.6.2.el6.x86_64] (local build)
Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net
=== START OF ...
After you accepted a bad answer, I am really sorry for my heretic opinion (which saved such arrays multiple times already).
Your second failed disk has probably a minor problem, maybe a block failure. This is the cause, why the bad sync tool of your bad raid5 firmware crashed on it.
You could easily make a sector-level copy with a lowlevel disk cloning ...
RAID controllers did not (and could not) synchronize disk spindles, but it was an option on some drives. Given a set of identical drives with spindle sync connectors you could ensure a set of disks were all synchronized. I happened to own some Seagate Elite 3 (ancient, obsolete SCSI-2 drives) which I remembered having such a connector so I found the ...
How to get the RAID information is going to depend entirely on the RAID controller you are using. Often, manufacturers will have tools that can be downloaded from their website which can be used to query the RAID controller and get this information.
In order to find which RAID controller you are using, try one of the following commands:
# lspci -knn ...
Or does everything still carry on as software raid automatically until the
faulty raid card is replaced?
How would that work? Would the software magically bypass the hardware raid, which acts as disk controller? Not only does the OS not see the disks, they are actually physically attached to the hardware raid controller. If the controller fails, then ...
The idea with ZFS is to let it known as much as possible how the disks are behaving.
Then, from worst to better:
Hardware raid (ZFS has absolutely no clue about the real hardware),
JBOD mode (The issue being more about any potential expander: less bandwidth),
HBA mode being the ideal (ZFS knows everything about the disks)
As ZFS is quite paranoid about ...
Why would you ask the internet about this?
There's so much WTF here, that I don't understand where to start!!
This question shows a fundamental lack of understanding of hardware, RAID arrays, storage, monitoring, and general IT best-practices.
I read this question and can't help but think:
Who is actually responsible for this server hardware? Where is ...
HBA just means 'host bus adapter', so it's anything that lets you connect to an external bus (although usually the term is applied to a something that lets you connect storage).
You might put one in to fit an external tape drive, or a SAN storage array. Usually, as in this case, it means the card isn't that intelligent. It supports only the simple types of ...
It's a waste of time.
You won't be able to induce failure or stress the drives in a meaningful manner. You have RAID, and that's a good start. Just make sure you have monitoring in place to actually detect failures as they occur and backups to protect against disaster.
Q. If one happens to have some server-grade hardware at ones disposal, is it ever advisable to run ZFS on top of a hardware-based RAID1 or some such?
A. It is strongly preferable to run ZFS straight to disk, and not make use of any form of RAID in between. Whether or not a system that effectively requires you make use of the RAID card precludes the use of ...
Just recently I read an article by one of Godaddy's engineers about this very topic: Learning to Deal with Learning
On their hardware (Dell PERC cards) battery learning cycle happens every 90 days, but no way to know when exactly it'll happen, ie during peak or off-peak hours.
They talked about different solutions:
Outright disable Battery Learning. Problem ...
This is an HP ProLiant server with a Smart Array P420i RAID controller. My immediate advice is to not change any of the default configuration settings unless you have a very specific reason to...
In short, don't worry about it.
The concept of sectors/tracks in the context of this controller and disk geometry isn't very useful here. Lots of layers of ...
It may not matter, depending on what your goals are... there are gray areas between both definitions - RAID controller and Host-Bus Adapter (HBA).
Understand that most high-quality servers have embedded RAID controllers today, so the need to select and shop for a separate RAID card has diminished as systems become more integrated...
RAID controller cards ...
RAID is just a name with a meaning that changed over time.
The important part is that the underlying technology and mechanisms are the same for the RAID levels, so you use the same controller (or piece of software, e.g. mdraid) to achieve all RAID levels.
the Raid Controller fails
I'm an electronics engineer, so my mental picture of the word "fail" may vary from a software engineers'... I mean, how often do you guys put on safety glasses for debugging?
If your RAID controller board has any kind of hardware failure which involves shorted MOSFETs, tantalum capacitors bursting into fireballs, power supply ...
All on-board caches are completely bypassed in JBOD mode. If you really need to use them you might want to look at a single-disk RAID0 config, which is unsupported but works with S2D as long as you patch "RAID" -> "SAS" BusType in registry.
(That's for VMware VSAN ...
Go ZFS. Seriously. It's so much better compared to hardware RAID, and reason is simple: It uses variable size strips so parity RAID modes (Z1 & Z2, RAID5 & RAID6) equivalents are performing @ RAID10 level still being extremely cost-efficient. + you can use flash cache (ZIL, L2ARC etc) running @ dedicated set of PCIe lanes.
This is a bug in some of the controllers that collide with iLO2 and there's a SIMPLE solution to that which always works.
Once you see the "Press any key to view Option ROM messages" message, click F8 and keep clicking it until you enter the iLO configuration screen.
Yes - iLO, not the P410.
Then, click exit immediately and start pressing F8 once it gets ...
Assuming you're on a recent firmware revision for the DL320 G6 server. You're going to have to pay close attention to the POST messages in order to catch the RAID controller's ORCA utility prompt.
The "Sea of Sensors" POST routine takes awhile from the first screen prompt (on a warm-boot) to step through RAM checks and to register the sensors. After the ...
Synched drives dont make sense any more for several reasons:
Disks have bad sectors relocated at production. Disks are huge, and have a number of defects after production, which are relocated. Therefore, two disks of the same production run will not be 100% in sync anyway.
Disks internally relocate bad sectors during use. These sectors get moved to ...
Yes, had that case.
Server "without UPS" in a data center (with the data center having a UPS). PDU failure - system crashed hard. No data loss.
And that basically is it. The good thing about a BBWC is that it is in the machine. Have a UPS - believe me, sometimes someone does something stupid (like pulling the wrong cable). A UPS is external. Oh, THAT cable ...
The accepted answer recommends the audacity that is yum install srvadmin-all. Blecch. Here's how to make it slightly less blecch-y (but still blecch-y nonetheless; you can get much leaner on HP's platform. But I digress...) By this I mean, only install those components necessary to manage storage on your machine.
BTW, the direct answer to the user's ...
You need a SAS expander and/or a server with a disk backplane that has an embedded expander...
RAID card w/1x mini-SAS connector : how do I physically connect 16 disks?
How exactly does a SAS SFF-8087 breakout cable work? + RAID/connection questions