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MSA1000 Raid 5 Performance - recomendations? What is a Port?

 
Phil Drapeau
Occasional Visitor

MSA1000 Raid 5 Performance - recomendations? What is a Port?

SAN Newbie here. We're about to configure a Raid 5 Set and we're wondering what the recomended number of disk per array is... more is better or less? The goal is performance. From what I'v read, more is better, ...I think. At the same time I'm told the old rule of thumb is no more than 8.

1 FCA 2101 on the host
1 Brocade Silkworm 3800
1 MSA 1000, w/14 72gb 10k drives

Firmware 2.38
256 mb Cache Total

Also, ACU says the MSA 1000 has 2 ports and 7 devices on each port... can someone explain exactly what a port IS?

Thanks in advanced!
2 REPLIES 2
Mike Naime
Honored Contributor

Re: MSA1000 Raid 5 Performance - recomendations? What is a Port?

Yes, more drives per raidset is better for splitting the load across several spindles. The number that you use is dependant on your paranoia level, and your willingness to restore from backups!

In this case your "port" is your SCSI bus. This is also refered to as a channel. Each channel in this case has 7 disk drives on it.

The MSA1000 that is in my data center has a potential of 4 channels if you add the 2 expansion shelves onto the cabinet.

The MSA1000 with initial 14 drive shelf has a split SCSI bus shelf that gives you 2 channels of 7 drives each. So, if you want to have your redundancy without potentially loosing ALL of your data. Then your only real option is to make 6 mirrorsets and leave 2 drives for spareset. (One spare drive per channel) Or make 7 mirrors if you are willing to replace a failed drive right when it fails.

I would not try a raidset on the MSA1000 without having the additional channels/shelves to accomplish this with. If you add the 2 expansion channels with either another split bus shelf, or single bus shelves. Then you can safely make a 4-drive raidset.

If you really need more than 4 channels. Look at the HSG80 controllers. They support 6 channels and 84 drives. Larger than that, and you are looking at the EVA that has up to 18 shelves/channels, or the XP type of system. Since I do not have an XP, I will not comment on it.
VMS SAN mechanic
Mike Naime
Honored Contributor

Re: MSA1000 Raid 5 Performance - recomendations? What is a Port?

On reviewing my last post, I forgot to mention that you can stripe your mirrors to get a larger drive while retaining your redundancy.

So, if you stripe 7 mirrorsets, you could get one LUN from this controller that had about 7x72GB (504GB) of space. (Minus formatting)
VMS SAN mechanic