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Is software RAID1 any good?

Is software RAID1 any good?

djvdorpdjvdorp Member
edited October 2012 in Help

I manage some Hetzner boxes which come with 2 large HDD's. They only offer Software-RAID 1 by default. I know software RAID is not like "real" hardware raid, but how are your experiences on this?

And, say I need the HDD space of non-raid (so combined diskspace), would I really be missing out? I personally dont have any trust in software raid so I feel like it shouldnt matter much, but maybe you guys have other opinions or experiences :)

I use http://tuxlite.com to configure all my VPSes and I love it!

Comments

  • In theory, shouldn't software RAID be more reliable, as there is no RAID Card to fail?

    SimpleNode | Minecraft and VPS Hosting | KVM and OpenVZ | Dallas, TX and Phoenix, AZ | PayPal and BitCoins accepted

  • @SimpleNode said: In theory, shouldn't software RAID be more reliable, as there is no RAID Card to fail?

    That is one way to think of it. The other way is, OS runs from HDD. OS manages Software Raid. HDD defunct, OS defunct, Raid defunct?

    I use http://tuxlite.com to configure all my VPSes and I love it!

  • In all software raid cfgs that I use, /boot is a RAID 1 across all four drives, so even if some die, it's still bootable provided one drive is intact.

    SimpleNode | Minecraft and VPS Hosting | KVM and OpenVZ | Dallas, TX and Phoenix, AZ | PayPal and BitCoins accepted

  • Software RAID in some cases can be faster and better. It depends on the kernel (any bugs / issues) and if CPU is important as it takes some CPU cycles away.

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  • @SimpleNode said: In all software raid cfgs that I use, /boot is a RAID 1 across all four drives, so even if some die, it's still bootable provided one drive is intact.

    If I remember correctly you're allowed only raid1 for /boot. But in grub you'll have to define a partition not an md since grub starts before the mdadm.

    To make all disks bootable you'll have to manually define them in grub. eg.

    root (hd0,0)
    setup (hd0)
    root (hd1,0)
    setup (hd1)
    
  • I try to avoid software Raid on my servers due to a nasty issue I experienced many times before. When a disk partially fails, the OS will try to access the bad sector for a extremely long time, stalling the disk I/O. The server is unresponsive until the OS finally drop the faulty drive. At next reboot, the delay will happen again. With Raid card, the faulty disk is dropped much earlier and I experience no further delay after reboot. I am now trying again a software Raid 1 on a new "experimental" server with two WD RED drives; I am hoping that this special drive firmware will avoid this kind of failure.

  • marcmmarcm Member
    edited October 2012

    @djvdorp I will say that software RAID1 is better than no RAID1 at all. You still have redundancy in case one of the drives fails. You won't have the features that a hardware RAID card offers, including write back cache (which should be backed by a BBU) and faster recovery times. Again, back to my original thought, I would say that software RAID1 one is far better than no RAID1 at all.

    @pcan I am on the fence about ordering a couple of WD RED drives from NewEgg. I have been using WD RE4 drives in my servers and my personal workstation, and I like those allot. Could you please share some of your experiences with the WD Red drives, how they are speed wise maybe? Thank you.

  • @pcan said: I am now trying again a software Raid 1 on a new "experimental" server with two WD RED drives; I am hoping that this special drive firmware will avoid this kind of failure.

    You'll be disappointed. They don't reduce raid failure rates - only drive failure rates. Error correction is the same as consumer models. WD RE is still a lot better I'd say. Performance is ok. I'd treat it as marketing gimmick more than anything.

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  • WD RE4 drives are the bomb, they work great.

    ~ Jimmy VortexUnit. Who likes poptart.cats?
  • pcanpcan Member
    edited October 2012

    @marcm: WD RED drives are a lot slower than RE4; they are at the WD green level. Here are some quick benchmarks on sustained transfer rate:

    software raid 1 on Windows with two WD RED 3TB: image

    Same server, hardware RAID5 of 4 WD RE4 GP (ecogreen) 2TB in a Sata to SCSI enclosoure, connected to a very old SCSI controller: image

    RE4 drives are faster than RE4 GP

  • @pcan

    Thanks allot for the benchmarks. So I guess no WD Red drives for me then.

    I would guess that:

    WD Green Line -> WD Red with different firmware and sticker WD Black Line -> WD RE4 with different firwmare and sticker

    Am I right?

  • You are basically right. Another difference is the extended warranty on RE4 and red. Red and green WD are physically identical. Black and RE4 have a slightly different exterior look, so there are some internal differences, I guess. I also found black drives more prone to failures than RE4, on my experience. The performance of red drives is enough for backups, but I would not use it for live storage.

  • I've used Linux software RAID 1 on desktops and LAN servers for 7 or 8 years and love it.

    It's better than no RAID. It's better than cheap hardware RAID. It's better than expensive hardware RAID if you don't have a spare, compatable RAID card on the shelf or there's an issue getting one.

    Linux software RAID is portable. Pull the disks out, put 'em in another box and boot.

    And it's flexible. If you've configured grub right, pull out ONE disk, put it in another box and boot.

    And It's resilient. I've never had a RAID issue that wasn't caused by a failing HDD. And in those cases I was able to replace the drive and rebuild the array without problems.

    If you've got the budget to do quality hardware RAID, go for it. If you don't, then software RAID might be a smart choice.

    Thanked by 1Brandon
  • @sleddog said: I've used Linux software RAID 1 on desktops and LAN servers for 7 or 8 years and love it.

    It's better than no RAID. It's better than cheap hardware RAID. It's better than expensive hardware RAID if you don't have a spare, compatable RAID card on the shelf or there's an issue getting one.

    Linux software RAID is portable. Pull the disks out, put 'em in another box and boot.

    And it's flexible. If you've configured grub right, pull out ONE disk, put it in another box and boot.

    And It's resilient. I've never had a RAID issue that wasn't caused by a failing HDD. And in those cases I was able to replace the drive and rebuild the array without problems.

    If you've got the budget to do quality hardware RAID, go for it. If you don't, then software RAID might be a smart choice.

    Well said and pretty much exactly what I would say.

  • @pcan said: Black and RE4 have a slightly different exterior look, so there are some internal differences, I guess. I also found black drives more prone to failures than RE4, on my experience.

    RE4 is based on Black with some tweaking - mostly firmware related.

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  • Thanks a lot all, nice summary @sleddog

    I use http://tuxlite.com to configure all my VPSes and I love it!

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