NASLite Network Attached Storage

I believe you can create a RAID 5 array from a minimum of 3 disks, however most common is 4. My 3Ware raid adaptor supports up to 12 disks, so I was wondering what is the ideal number of drives, if considering performance and storage efficiency.

Does NASLITE 2 support RAID 50? (that is two RAID 5 arrays joined like a RAID 0, to get speed and protection).

RAID5 requires a minimum of three disks - I would not say that four is more common, but that's just my opinion, you're entitled to yours.

I don't think there is an ideal number of disks for an array - this may depend on the intended use of the array. As an example - transactional databases typically have large numbers of small reads & writes, and RAID5 is generally considered as not suitable, RAID1 being the preferred choice. To go to the other extreme, disk-to-disk backup would have a much lower number of large writes, and storage efficiency would be more the focus.

Another important consideration when building large arrays, especially with today's larger disks is the rebuild time. The more disks in an array, the greater the probability of an array member failing, and with the longer rebuild times required by the larger disks, the possibility of a second disk failing and trashing the array is increased.

Newer RAID controllers now offer double parity RAID, also known as RAID6, uses two disks worth of space for parity information, and can survive the simultaneous failure of two members. I believe HP calls this Advanced Data Guarding or ADG.

The way NASLite-2 seems to work, it's not a question of whether or not it supports RAID50, but whether or not your RAID controller supports it - as far as I know NASLite-2 is completely unaware of the physical disk structure of the array, the RAID controller will present the array as one or more logical disks, and that is what NASLite-2 sees.

This is correct, since NASLite only supports hardware raid it's completely unaware of the raid level the card is set at, it just see's it as one big drive.

Thanks for the replies.

How does NASLITE handle recovery after a failed drive, then? Is that done entirely by the raid adapter's bios?

The raid card bios will rebuild any failed drives at that level, NASLite will repair any filesystem level problems.

Good news: I built 2x RAID 5 arrays with 4x400 GB drives and NASLITE 2.04 USB.

Bad news: After copying back my data (about 500 GB) to array #2, one of its hard disks had dropped out. The 3ware RAID adaptor is currently re-building the array.

The question: While the rebuild is happening, not only can I not access array #2, but even array #1 is out -- in fact NASLITE is stuck on "Checking storage filesystem (Disk-1) [BUSY]" and I can't talk to the Naslite server at all! I would have expected the Naslite OS and array #1 to work and even secretly hoped that array #2 would be at least readable or accessible as a degraded array. Is what I am seeing "working as designed"?

I can't comment on "working as designed", but I would say I believe it's working as I expect it to.

Let me start by asking - are you using an enclosure that supports hot swap of the disks or did you power down, replace the failed disk and then restart?

If it's the latter, then I believe what you're experiencing is to be expected.

Based on my experience with RAID, mostly in a Windows environment, a failed disk should not bring the system down or prevent it from booting (although you should get a logical drive impaired or degraded warning that might require you to press a key or two).

What happens when the failed drive is replaced will depend on the particular hardware and conditions - if the hardware supports hot swap, and the drive is hot swapped, I would expect operation to continue as normal although there might be some performance degradation.

If the drive is not hot swappable, or the system is shut down and the drive replaced, the user will typically have to manually start the rebuild, either from the RAID BIOS or from the RAID management utility after rebooting into the OS - the latter course of action is preferrable if available, as the RAID BIOS may not allow you to exit during the rebuild, or as I believe is happening in this case, not allowing access to the arrays during the rebuild.

Im currently running a RAID-1 with 2x 250GB disks on an LSI-Megaraid SATA 150-4. I'm planning to expand this into a 3x 250GB RAID-5, is there anyway to do this without wiping the drives - storing the current data elsewhere until the RAID-5 is setup?

The short answer is NO.

Reason is that in RAID 1 the drives are mirrored. That is both look like single drives. In RAID 5 the data and parity is striped across the array. Each of the drives contains part of every byte of data. i.e. they have to be re formatted and rewritten and are therefore wiped before being created. You will have to have another place to store all data while you are doing this.

Hope that helps.

My answer to this would be - it depends - on what features your particular RAID hardware, AND the OS you are using allows.

There is RAID hardware that will let you change RAID levels on the fly, but if your OS does not have support for the feature you will be unable to use the facility.

As far as I am aware NASLite does not support this, so you regardless of hardware features, you will need to store your data elsewhere whilst you recreate the array.

Just wanted to let you know that it did indeed work well to reconstruct the RAID1 to a RAID5 without any temp storage solution. However NASLite did not detect the new space so I had to boot with Gparted and expand the partition. After that everything was hunky dory! Glad to have the expanded space but I miss the RAID1 rw performance *sniff*