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1

If this is a desktop system, this will likely get marked as off-topic and redirected to SuperUser - FYI. More hardware specifications would be needed to answer with any degree of certainty (what motherboard, which PCI slot the card is in, etc). However, that LSI card may well be the performance bottleneck. I would suggest you set up a single-drive RAID0 ...


1

This is most likely possible, though it depends on how you've implemented RAID. If you're using Linux software RAID (e.g. mdadm), live RAID type conversions are definitely possible. If you're using hardware RAID in a server, most modern RAID controllers support live RAID type conversions... Though you'd want to check the user manual for the particular ...


1

If your RAID5 is running in degraded mode it should allow access to your data. But since it doesn't I suspect the problem may be at the filesystem level. Try and ssh into the QNAP and see if your data volume is mounted or not. The QNAP uses Linux Software RAID aka mdadm. To gather info take a look at /proc/mdstat and do some mdadm --examine's on the RAID ...


1

The drivers are part of the kernel, they do not require separate installation. If there were no drivers, the disks would not even be visible on the system. Yes partition sizes will need to grow if the underlying storage grows. You should use LVM if you plan to do this, otherwise the system will need to be taken offline to grow the partition. /dev/sdxx is ...


0

Depending on the controller firmware, there are usually two ways of doing this. Some controllers offer a "JBOD" setting that passes the individual disks though. Other controllers require you to set up a bunch of single disk RAID0 groups, which essentially does the same thing. Just a little more work. I couldn't find instructions for that particular ...


2

The main advantage of hardware RAID is the protected write back cache which will boost performance when dealing with synchronized writes (eg: databases). Your should absolutely avoid RAID cards without protected write back cache, as they often are much slower than software RAID. At the same time, not all RAID controllers play well with SSDs. The main reason ...


8

Yes. You must use kexec-tools. To make the life easier, I use kexec-reboot. $sudo apt-get install kexec-tools $wget https://raw.githubusercontent.com/vadmium/kexec-reboot/master/kexec-reboot $chmod +x kexec-reboot $sudo mv kexec-reboot /usr/local/sbin/kexec-reboot $sudo /usr/local/sbin/kexec-reboot


1

Linux software RAID (md) supports passing discard ops down to its components. When those components are SATA devices, they turn into ATA TRIM commands. See for example: Implementing Linux fstrim on SSD with software md-raid Depending on your access pattern, 2x SSDs concatenated could be as fast as RAID0. e.g. random IO scattered across the entire disk ...


6

With SSD's the only generic recommendation is to buy the right drive for your workload. See this answer for the rationale. The warranty for the Samsung SSD 850 Pro may be ten years, but that covers mechanical failures and does not cover you when you exceed the still "somewhat limited" total write capacity limit. Associated with the failure rates and ...


2

4xSSD(512Gig) in a RAID10 you have redundancy (+) you have only 1TB of usable space (-) you have x2 speed (+) 2xSSD(1Tb) no redundancy (-) you have 2TB of usable space (+) you have normal speed (N) 2xSSD(1Tb) RAID0 no redundancy (-) you have 2TB of usable space (+) you have x2 speed (+) As for the lifetime of them, that model is pretty good, ...


65

I use kexec-reboot on all of my production systems. It works well, allowing me to bypass the long POST time on HP ProLiant servers and reduce the boot cycle from 5 minutes to 45 seconds. https://github.com/error10/kexec-reboot


15

Yes, it is possible. kexec will allow a Linux kernel to be booted directly from Linux without going through the BIOS boot process.


0

You need to use the integrated version found here: http://www.dell.com/support/home/us/en/04/Drivers/DriversDetails?driverId=FNPHT Unfortunately, it let me delete all the partitions but not install windows from a flash drive. It saw the disks individually (not the logical disk from the RAID) but would not allow installation on either disk. Tried the ...


1

Nope. HP controllers don't offer a mixed mode like what you're asking for. Which specific server model (and storage controller) are you planning to use? If you buy a DL3x0p series Gen8 server with an onboard P-series RAID controller, there is a secret "HBA" mode that will disable all RAID features. If you buy a DL3x0e series, there are some messy storage ...


1

This configuration doesn't appear to be validated/tested by Dell, so it would technically be "unsupported". I've not seen any postings around with test results indicating one way or the other, but LSI's compatibility document for the 9266-8i (based on the same 2208 ROC) Indicates that the R710 is in fact compatible with this "generation" of cards. If ...


0

Assuming your servers are under warranty, I would say call Dell and see if it's supported.


1

Eventually (after days of exploration) I managed to force the array to work and to copy the data. First, the cause was disk bad sectors - I suppose in the area of raid superblock and/or partition table. Second, I had to use dmesg to see errors during mdadm --assemble or mdadm --create: [Thu Mar 19 23:27:04 2015] end_request: I/O error, dev sdc, sector ...


0

This just doesn't work. I'll accept that the documentation which influenced the decision to buy this solution was flawed and that the HP Smart Array B320i RAID controller is not capable of logical drive expansion, migration or modification. It's a shame. In this specific case, I had to rebuild the server in order to add a new disk to the array set.


0

I have a Adaptec card running just fine with the HP DL320e and the new trays. It does show the drives working, but of course not any of the other led indications. But I am having some trouble right now to swap the standard cable for a longer one to the backplane... so maybe there is something going on there... but not sure what that would be... looks like a ...


0

On thing that looks quite suspicious is the overlap of two partitions: /dev/sdq3 588 91201 727848912 f Win95 Ext'd (LBA) /dev/sdq5 589 91189 727744480 fd Linux raid autodetect I assume you are wanting to access /dev/sdq5? What is the /dev/sdq3 entry doing? Try using fdisk -l -u=sectors for a more precise view ...


2

If using FreeBSD (also FreeNAS) read speed is better. Source: http://open-zfs.org/wiki/Features#Improve_N-way_mirror_read_performance Linux/illumos/OSX does not have that patch which rebalances read I/O to the least busy device, instead it's just round-robin. With these, you will still get a performance boost with a n-way mirror vs. single drive, but in ...


1

This depends on the ZFS implementation and the Hardware you are using. These benchmarks https://calomel.org/zfs_raid_speed_capacity.html provide a quick overview of the mirrored/striped performance, measured on FreeBSD. As you can see, the read performance is doubled with SSDs and increased by approximately 50% with HDDs.


5

I am going to try and sum up my comments into an answer. The basic line is: You should not tinker with the strip size unless you have good evidence that it will benefit your workload. Reasoning: For striping, you have to choose some strip size and 64 KB is the default the manufacturer has chosen. As the manufacturer (LSI in this case, rebranded by Dell) ...


1

While it makes sense in theory, the data doesn't support the need to work in your drive. Not only will a few weeks not really make an impact, the failure percentages don't really work when looking at only two drives. While there has been some indication of more normalized failure rates when it comes to drives of the same model. Most age-related results ...


2

The general rule of thumb with RAID10 is that smaller chunk size give you fast sequential transfer in a wider range of cases, while larger chunks provide higher IOPs and higher sequential speed in selected scenarios. Your expected workload (Virtual Machines) are all about issuing small-to-medium (< 256KB), pseudo-random requests. In other words, you need ...


0

Yes, you should be concerned. Not extremely concerned, but investigate it and - if necessary - replace some parts. SCSI errors are usually generated by: problems with drivers/firmware or hardware faults. Refer to: http://en.wikipedia.org/wiki/Key_Code_Qualifier At minimum though, a SCSI error means 'something went wrong'. This may only be a minor ...


0

You need to check up on parted. I think you need to do something like this: parted /dev/hda set <partition number> bios_grub on quit Once you have that going, grub should be able to figure out where to put stuff. Then do this - or your own variation: grub-install --modules=raid --no-floppy /dev/sda This should make grub work again. I found lots ...


0

You can do, but it won't help too much. For example, if there is a needle in the input power, the same needle will kill both disks. What is important: you need to have a good backup. Raid doesn't make up for a good backup. Actually, if you have a good backup, maybe a mirroring raid isn't surely needed (if you can tolerate a system collapse once around 2-3 ...


0

This is usually an argument for SSDs more than HDDs in my experience. SSDs have limited write cycles, therefore if you use a RAID1 with two SSDs of the same model, both should run out of write cycles near the same time. As for general failures, unless you have a serious issue like mass vibration, static, or high heat; I don't suspect you'll see 2 out of 2 ...


1

Great Question - However, unlike automobile headlights, this is a waste of time. The MTBF [mean time between failures] rating for 4 GB drives [WD Red in this example] is 1,000,000 hours. The odds of two drives going bad in a mirror at the same time is extremely rare. When I have seen this happen, it is has been because the first drive failed without ...


6

It may be better to use different brands or series of disk together if you're worried about this. I have seen disks of similar type and age fail in clusters, so IMHO it's not an urban leend.


16

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.


1

So I answering my own question for everyone's benefit who has to deal with these type of fake raid controllers. Here is what I did: 1, Zero the superblock out on the second disk (sdg) which was written into it by the raid bios at start mdadm --zero-superblock /dev/sdg 2, Now interestingly the md126 is not the main raid array: mdadm -Q --examine ...


1

After hours of Googling and some extremely wise help from JyZyXEL in the #linux-raid Freenode channel, we have a solution! There was not a single interruption to the RAID array during this process - exactly what I needed and expected from mdadm. For some (currently unknown) reason, the RAID state became frozen. The winning command to figure this out is cat ...


0

I had the exact same status: NAME STATE READ WRITE CKSUM RAIDZ0_01 DEGRADED 0 0 0 raidz1-0 DEGRADED 0 0 0 gptid/4fb5f83e-91b1-11e2-923c-000c292ee274 ONLINE 0 0 0 ...


0

The solution was the following: # Load modules modprobe md modprobe raid1 # Detect raid arrays by superblocks and generate config file mdadm -E --scan > /etc/mdadm.conf # Assemble arrays from config file generated above. mdadm -A -s If the modprobe above fails the module was probably included in the kernel.


2

Since noone said it directly enough: Raid6 write performance is not marginally worse. It is horrible beyond description if put under load. Sequential writing is OK and as long as caching, write merging etc. is able to cover it up, it looks ok. Under high load, things look bad and this is the main reason a 1+5/6 setup is almost never used.


1

Seek times The issue is that, the write seek amplification behaves very differently to the write throughput amplification. The minimal write throughput amplification with parity occurs when an entire stripe is written at once (let's call this adjective ‘full-stripe’) yet the minimal write seek amplification occurs, conversely, when the entire write ...


0

As an example I have a NAS running G1830 8GB RAM Areca 1220 Card set to 80% background tasks for expansion. 8 x 2TB Samsung 5900 RPM disks. I just expanded from 7 to 8 drives, which took 21 hours. I imagine that a 7 disk rebuild would take about that with similar specs. It really comes down to the speed of the CPU on the RAID card, and the individual ...


0

In Synology terminology a disk group is simply a RAID array that can then be split it up into several volumes. So if you have 4 disks, you can create one single disk group (RAID array) and create two volumes from it. Or you could create 2 disk groups, and create one volume on each. The difference / advantages being that the single array will have more ...


3

Modern and advanced systems don't implement shapes like that because they're excessively complicated, completely unnecessary, and contrary to any semblance of efficiency. As others have pointed out, the ratio of raw space to usable space is essentially 3:1. That is essentially three copies (two redundant copies). Because of the calculation cost of "raid6" ...


11

You have diminishing returns on reliability. RAID 6 is pretty unlikely to compound failure even on nasty SATA drives with a 1 in 10^14 UBER rate. On FC/SAS drives your UBER is 1 in 10^16 and you get considerably more performance too. RAID group reliability doesn't protect you against accidental deletion. (so you need the backups anyway) beyond certain ...


11

You may need to understand a bit more about RAID-6; I recommend reading Wikipedia's explanation. The problem is that the second parity bit in RAID-6 isn't just a copy of the first (simple, XOR-style, as used in RAID-5) parity bit; that would be completely useless, because in the event of losing two data drives the fact that you have two surviving copies of ...


14

The practical answer lies somewhere at the intersection of hardware RAID controller specifications, average disk sizes, drive form-factors and server design. Most hardware RAID controllers are limited in the RAID levels they support. Here are the RAID options for an HP ProLiant Smart Array controller: [raid=0|1|1adm|1+0|1+0adm|5|50|6|60] note: the "adm" ...


16

Generally I'd say RAID 1+0 will tend to be more widely used than 1+5 or 1+6 because RAID 1+0 is reliable enough and provides marginally better performance and more usable storage. I think most people would take the failure of a full RAID 1 pair within the RAID 1+0 group as a pretty incredibly rare event that's worth breaking out the backups for - and ...


0

I'm sorry. With a single host, you won't have any proactive monitoring or email/SNMP alerts available for this system. You can install the LSI or Dell Offline .VIB bundle to at least get hardware RAID health status to show up in your vSphere client.


0

Yup, so long as only a single disk has failed, you can just pull the blown disk, pop in a new one and the array should start rebuilding itself right away. I suspect that Dell has created a VIB that you could load into ESXi that would give the Hardware tab greater visibility into your RAID config. I know HP does this, so hence why I suspect Dell would too. ...


0

Your software raid is taking all the CPU cycles in order to run the RAID. Getting a hardware RAID can help. Keep in mind that if you want to take full advantage of a RAID controller you will need to ensure it has a BBU (battery back up) in order to enable the cache and write-back mode. Depending on what is important to you, you could turn on RAID 0 ...


2

Late reply, but couldn't you do what I have been doing for some time? I use 2-drive RAID1 installs for most of my servers. The way they are set up is md0 is mounted as /boot and is a roughly 250MB raid1, while md1 is mounted as / and is the remainder of the drive's capacity excluding a swap area on each drive. Like this any changes to /boot are mirrored ...


0

1) Yes it's possible to lose what's on the disks already but generally people don't change RAID levels mid-production. 2) Press F5 during disk controller boot to load ACU and create a R1 Mirror - that's all - should say '1 Logical Disk' at controller boot. 3) Just DD it off somewhere or reinstall.



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