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9

These raids are all relative to each-other assuming the same disks and controller in the array. Raid5: Good read speed, rotten write speed, can survive any double disk failure if the failures occur over enough time for the raid to rebuild between failures. (ie disk fails, raid rebuilds, disk fails, you're okay). If you have simultaneous double disk ...


9

There's lots of similar questions/arguments on this site regarding R10 vs. R5/R6 but they boil down to "exposure during rebuild". The argument for R10 over R5 is strongest when dealing with the larger, slower disks some buy because their GB/$£€ is better (i.e. 2/3TB 7.2k SATAs) as arrays of these disks can take literally days to rebuild following a disk ...


8

Whoever told you that RAID 10 is somehow inherently slower than RAID 1 doesn't know what they're talking about. That makes the rest of the question unanswerable as it's based on a false assumption. Further reading: What are the different widely used RAID levels and when should I consider them?


8

Each drive adds its performance to the sum, so more drives will be faster than less drives, all else being equal. The size doesn't directly have an effect, though. If you have a choice between 2.5 inch 300GB 10k RPM drives and 2.5 inch 900GB 10k RPM drives, they'll perform about the same, drive for drive. The difference is when you figure it per TB. So 10 TB ...


7

It's 10 (1+0), rather than 0+1 - because mirrored stripes are more likely to handle multiple disk failures than striped mirrors.


7

RAID10 with 4 drives will be quicker -- the extra spindles mean that twice as many IOPS can be handled (more or less).


7

You may have misunderstood someone. RAID-5 is slower than RAID-10 on writes, but RAID-1 can be treated as a RAID-10 with a single pair of disks, and thus has the same performance per "spindle" as RAID-10. The best recommendation for SSD on a database is to use RAID-5. The rebuild time on the incredibly small and fast SSD drives is very good. Since you'll ...


7

Each drive can do 180 random IOPs. Is your workload totally random? I bet what you're seeing is sequential reads/writes.


6

As Chopper said, a striped data format will make it slightly less convenient to recover data from your drives. If you're RMAing the drives, you absolutely cannot count on any sort of wipe operation to do much good, since the most likely failure mode prevents you from reliably writing to some sectors, and the other failure mode prevents you from verifying ...


6

It makes no sense no, R10 would be better, but you should really try to have enough real memory to not have to care.


6

Your Volume Group isn't using the entirety of the extents created for it: VG Size 149.94 GiB PE Size 64.00 MiB Total PE 2399 Alloc PE / Size 1171 / 73.19 GiB Free PE / Size 1228 / 76.75 GiB You can add more extents using the following command: lvextend -l +100%FREE /dev/mongodb_vg/mongodb_lv /dev/md0 ...


6

The exact number, or even a reasonable estimate, would be impossible to guess based on this information. Many server grade disks have published number; but the RAID system may or may not take full advantage of the disks. The RAID HBAs generally also have some published benchmarks. Extrapolating from these is the best guess you'll get without testing an ...


6

Yes, this will work. Of course, don't expect to get any performance gain as the underlying disks are on the same device, but it's a great way to learn how to set it up in a safe environment.


6

You can't use non-HP SSDs in HP ProLiant servers like this. Just because this worked on your G7 server doesn't mean it is okay for your Gen8 ProLiant servers. (basically, why buy enterprise gear, then cripple it with incompatible components?) Please see: 3rd party SSD drives in HP Proliant server - monitoring drive health or Third-party SSD solutions ...


5

I believe RAID10 support (through the fancy all-in-one RAID10 driver rather than doing a RAID0 of RAID1s) is not present in the installer for Etch or Lenny, but it has been added for the current development version so will be in the next release (or available now if you don't mind using the testing distribution, but this is not recommended in a production ...


5

I don't think so. Desktop versions of Windows will only support RAID-0 in software, mainly for applications like editing streaming media. Windows 2003 (and IIRC 2008) will support RAID-1 and RAID-5 in sofware but not RAID-10. Note that Software RAID support in Windows is generally poor - much poorer than that found in Unix or Linux. You are much better ...


5

I'd have to disagree with CHopper3. Since there are only 4 drives in this situation your failure capabilities are the same (2 drives) with either scenario, except with raid 10 if you happen to lose the wrong 2 drives then you'll have a real problem. Also there is definitely an added benefit of having a global spare for your other RAIDs as well.


5

I would go 10/2. Logs are usally small and sequential, and your RAID controller should be able to queue them efficiently enough to write them onto 2 disks in raid 1 without disturbing the rest. If your RAID controller can't do this then forget about any split and just go 12 if you are in a hurry. If you've got time run some tests and see what works. ...


5

I got explanation from guys on VMWare forum in thread http://communities.vmware.com/message/2012333 . And the reason is that ESXi does no caching and completely relies on the controller for writing data to disks so speed 20MB/s with write-through cache mode (only mode this controller supports as it does not have BBU) is standard. Hyper-V is apparently doing ...


5

RAID 6 or RAID 10. RAID 10 is a bit of a capacity waste, and RAID 6's random write penalty is completely hidden behind the write cache. I know you only think you'll need 4TB, but there's no reason to waste.


4

What is the downtime tolerance of the array? Is it physically close, or in a remote data center? Bascially, if you can tolerate it, a cold spare allows you to do RAID10. The spare is sitting close by, but you have to physically do the swap. If that is not an acceptable scenario, then RAID5 with a hot spare is the only answer left. Since you already have two ...


4

Unspared for sure. That mirror is at risk, where the mirror that is rebuilt with the hot spare is redundant.


4

Backup the server and test the backup Update the server - BIOs, PERC firmware, disk firmware - everything (contact Dell support for help with that) Go into OMSA (install OMSA if you don't have it - Dell support can provide a link) In OMSA go to the Logical Disk, from the drop down menu choose "reconfigure" and if you have enough drives, it will let you ...


4

My understanding is that raid1 doubles the writes,but can speed up the reads a lot. How large is your database and how fast can you make backups of it? I also thought RAID0 (striping only) made it MORE likely you could have a problem,i.e. one volume is lost and its good bye data. One of the unexpected I/O oddities of Ec2 EBS volumes, is the first time you ...


4

As the others have said, buy more ram. However Chopper3's answer is not exactly correct. Given that both provide fault tolerance, and leaving aside capacity, the reason for choosing one over the other would be all about performance - and that depends on the workload. For a system with few processes but big memory requirements (e.g. AI engines, FEA) then you ...


4

/boot needs to not be encrypted otherwise the boot loader (unless I'm behind the times and one of them supports encrypted volumes) will not be able to ready the Kernel and initrd. It does not need to be encrypted as it should never contain anything other than the kernel, the initrd, and perhaps a few other support files. The the device that is your LVM PV ...


4

Yep, called mirror-splitting, assuming you have a HP E/P-class controller - just remove (the right) two disks from server1 , replace them with two blanks, that'll then rebuild. Meanwhile boot server 2 from JUST the two disks you removed from server 1, wait for boot to finish (it'll error like crazy) then stick two blanks in server 2 and again wait for ...


4

Windows software RAID doesn't support RAID-10. I've never heard of third-party drivers for Windows software RAID and, frankly, I think I'd be afraid of them if they did exist. (They'd have to be debugged and battle-tested before I'd even think of using them...)


4

First of all hdparm is not a real benchmarking utility, it isn't nearly rigorous enough to demonstrate true performance. Better tools are iozone or iometer. Secondly, your results can be explained with one observation. Number of disks matters. Consider this: Your R0 test had 6 disks involved in reading. Your R1 test had 1 disk involved in reading. ...


4

Yes. As of mdadm version 3.2.1, and running a "suitably recent kernel" (whatever that means, I'd guess at least 3.0), a reshape from RAID10 to RAID0 is possible. This means a pretty recent Linux distribution; the system that you're running on may need an upgrade, or you may need to temporarily boot to a live CD type of environment with newer tools to do ...



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