Recycling drives in P2000

[Eric W. Bates]

We're building our first SAN. We are considering a P2000. We have 3 DG180 G6 machines with 3Gbps SAS drives. Since those machines will no longer need their own drives, it seems efficient to move the drives from the DG180's to the P2000 enclosure. The P2000 has a 6Gbps SAS bus so obviously this will be less efficient.

Thots? Comments? Considerations?

Thanks for your time.

[Trygve Henriksen]

3Gbps/6Gbps doesn't really matter all that much as long as you stick to one or the other.

The fact is that it's reading the data off the spinning platters that's the slowest operation. (Well, writing is slower... )
What matters more is that they have the same RPM rating(preferrably as fast as possible) and use the same tecnology. (Dual-port SAS is good :-)

You will have to make darn certain that the disks all use the same Firmware level, though, or you'll be in a world of hurt before you know it.

Also, there's no promise that the arrays you have created can be transplanted to the P2000 and recognised. You will most probably have to either create a new array(using new disks) first and copy over data from one of the old arrays, then reuse the disks from that array for the new second array and so on...
Alternatively, you could move the disks, recreate the arrays, then restore data from backups. (I wouldn't recommend it... Lots of downtime, lots of things that can go wrong)

How large arrays do you have,(number of disks, their size, RAID-level, hot spares)

[Eric W. Bates]

Yah, I assumed I would be rebuilding the arrays from scratch. I didn't even want to try transplanting them. This is nothing more than an attempt to avoid the need to buy $5000 worth of new spindles and basically chucking all the ones we've already bought.

What we've got is 3 identical machines (I just finished a marathon of flash updates) and they all report that the drive firmware is HPD8. All drives are part #DB0750BABFE: 750 Gb dual port SAS 7200 RPM. All 3 are configured RAID 5 with 1 spare spindle. All 3 are running ESXi and have several VM's running.

The plan is to work over the weekend. Dump the vm's to interim storage, move the physical drives, build a whole new array, mount the new partitions back on the servers, and copy the vm's back from interim storage.

The concerns I can imagine:
--It just won't work. The drives have something missing and simply will not be recognized on the P2000.
--I'll be locked into 3Gbps/7200 RPM drives if I want to expand the SAN with additional enclosures.
--Performance will suck. 6Gbps really does make a significant difference over 3Gbps even with 1Gbps NICs.

[Trygve Henriksen · Accepted solution]

Those drives should work just fine, but...

With 750GB disks, I would REALLY recommend using RAID6 instead of RAID5 as rebuild time is 'forever and a day' on such large disks.
(It took about 8Hours to rebuild a failed drive in an array of 600GB disks in my MSA2324fc. That's 8Hours without protection. That array doesn't contain 'user data' so I can live with it. All 'user data' is on arrays of 300GB disks... A lot of them... )

[Eric W. Bates]

RAID 6 is probably good advice. Thank you.

Since additional enclosures for a P2000 are attached via SAS cables, can I add additional arrays with different type spindles; or would using the 3Gbps 7200 RPM drives lock me into that for all future adds?