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RAID Card advice


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Posted

Hey all,

I'm after some advice on RAID cards, or alternatively if there is a better way of achieving what I'm after feel free to throw that into the mix.

Put simply I'm after backing up a 12TB (6*2TB physical discs) raid 10 volume across a further 6 1TB discs (I forget my raid assignments but that is raid 0 or JBOD that I guess I'll be using - will check them out)

I am currently managing with the backup split over 4 1tb drives that are just individually plugged into the PC mobo and data copied/synced across. As time has progressed and work continues to be ever more demanding on space we have maxed out a 1TB share - I.e. a whole backup drive is taken up by one share, this now obviously leaves us with the problem of splitting files and folders across physical drives. Not ideal.

Plus there are no more sata ports on the mobo!

Key points:

Source raid is a NAS box - relatively heavy usage.

Backup machine needs only light use from itself - no shares.

Any suggestions on method, card, onboard processor, cache - just generally what to look out for is massively appreciated :)

Oh, and budget around

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Posted

Get a IBM ServeRAID M1015 - can pick them up (mainly from ebay) for about

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Posted

Fahim, cheers for that. Just been having a look at it and from what I can see it looks ideal!

Have a few questions if you have the time.

As I understand it the M1015 is the controller and may be present on differing cards (??) see: http://www.servethehome.com/ibm-m1015-part-1-started-lsi-92208i/. Are there any specific brands I should look out for in terms of quality and reliability.

From a little further research JBOD is not what I need, as it still presents drives as individual. Hence I was looking at SPAN or RAID 0. What are your opinions in using RAID 0 for a backup?

- as a side note I found that RAID 0 uses little processing hence no need for onboard memory or processor, bonus!

If there is a power failure will this cause RAID rebuild or data loss, how have you found its reliability?

Cheers,

rancid

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Posted

As I understand it the M1015 is the controller and may be present on differing cards (??) see: http://www.servetheh...ted-lsi-92208i/. Are there any specific brands I should look out for in terms of quality and reliability.

The controller is a LSI SAS2008 ROC controller. I would guess the LSI version is the best to have, but I have the IBM and have had no problems with it so far. There are other rebadges too. I've found the IBM version cheaper for some reason, even if you include the Feature Key to make them functionally equivalent.

From a little further research JBOD is not what I need, as it still presents drives as individual. Hence I was looking at SPAN or RAID 0. What are your opinions in using RAID 0 for a backup?

I wouldn't - I'd go RAID5 (preferably with a hot-spare) or RAID6 (ideally with a hot spare). For RAID5, it amounts to one drive to store parity.

If there is a power failure will this cause RAID rebuild or data loss, how have you found its reliability?

I don't know. I've not had a power failure since using the card.

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Posted

Fahim, cheers for that. Just been having a look at it and from what I can see it looks ideal!

Have a few questions if you have the time.

As I understand it the M1015 is the controller and may be present on differing cards (??) see: http://www.servetheh...ted-lsi-92208i/. Are there any specific brands I should look out for in terms of quality and reliability.

From a little further research JBOD is not what I need, as it still presents drives as individual. Hence I was looking at SPAN or RAID 0. What are your opinions in using RAID 0 for a backup?

- as a side note I found that RAID 0 uses little processing hence no need for onboard memory or processor, bonus!

If there is a power failure will this cause RAID rebuild or data loss, how have you found its reliability?

Cheers,

rancid

RAID 0 offers no redundancy, which is why it doesn't require any extra work on the RAID card processor or memory, and can result in data loss. As long as you don't have a write back cache activated without using some sort of Battery Backup Unit you shouldn't have to worry about massive data loss on a power failure (so long as the drive survives the power outage). If you do lose a drive though you won't be able to recover at all.

RAID 0 is great for when you need very fast reads speeds and can tolerate the data being lost completely due to a drive failure. An example could be an OS drive where actual data is stored on a RAID 5 volume or such. Basically, if you need it to survive a drive failure don't put it on a RAID 0.

That being said, no RAID level is an excuse for not having a backup. A RAID 5 can survive a single drive failure, but it can't survive two drive failures happening before the spare drive has been brought up to speed, for instance. No RAID level will protect you from an accidental deletion or a rogue program or operating system or drive bug corrupting your data. Keep all of this in mind.

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Posted

The controller is a LSI SAS2008 ROC controller. I would guess the LSI version is the best to have, but I have the IBM and have had no problems with it so far. There are other rebadges too. I've found the IBM version cheaper for some reason, even if you include the Feature Key to make them functionally equivalent.

I wouldn't - I'd go RAID5 (preferably with a hot-spare) or RAID6 (ideally with a hot spare). For RAID5, it amounts to one drive to store parity.

I don't know. I've not had a power failure since using the card.

I see, getting there with the understanding now.

RAID 0 offers no redundancy, which is why it doesn't require any extra work on the RAID card processor or memory, and can result in data loss. As long as you don't have a write back cache activated without using some sort of Battery Backup Unit you shouldn't have to worry about massive data loss on a power failure (so long as the drive survives the power outage). If you do lose a drive though you won't be able to recover at all.

RAID 0 is great for when you need very fast reads speeds and can tolerate the data being lost completely due to a drive failure. An example could be an OS drive where actual data is stored on a RAID 5 volume or such. Basically, if you need it to survive a drive failure don't put it on a RAID 0.

That being said, no RAID level is an excuse for not having a backup. A RAID 5 can survive a single drive failure, but it can't survive two drive failures happening before the spare drive has been brought up to speed, for instance. No RAID level will protect you from an accidental deletion or a rogue program or operating system or drive bug corrupting your data. Keep all of this in mind.

and @fahim

Very interesting comments. Nice to know about the power failure situation.

In terms of the RAID setup I'm not necessarily after speed. After all, the data is literally going to be used as just a backup of an existing RAID 10 array. - With the occasional exception of relatively light use (one person on machine locally).

That being said it doesn't necessarily need to survive a drive failure, assuming they both don't fail at the same time....:-P

Now I am in a quandry, with RAID 5 or RAID 0. The way I see it RAID 5 will not provide my total volume necessary using the 6 drives I have. Not necessarily a deal breaker as the card can cope with a couple of extra drives. But it does add to the cost, drives + advanced feature set key. On the plus side I gain a one drive failure redundancy.

In terms of RAID 5 speed, what are we talking about on this card. Bearing in mind no on board processor/memory?

Cheers,

rancid

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Posted

In terms of RAID 5 speed, what are we talking about on this card. Bearing in mind no on board processor/memory?

The ROC is an on board processor (it's a PowerPC chip from what I understand), but the M1015 doesn't have a cache, or battery backup (which makes sense, given no cache).

As for performance you can read http://www.servethehome.com/ibm-serveraid-m1015-part-2-performance-lsi-92208i/

I guess performance largely depends on how good the attached drives are. I personally have enterprise grade 7200RPM 1TB SATA drives (4x3.5 WD RE3 + 4x2.5 Seagate Constellation ES.2) attached and am quite happy with the performance.

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