Questions on Partitioning across two drives
Jim
mickeyboa at sbcglobal.net
Mon May 11 15:05:04 UTC 2009
Kevin J. Cummings wrote:
> Jim wrote:
>> Kevin J. Cummings wrote:
>>> Jim wrote:
>>>> Patrick W. Barnes wrote:
>>>>> On Sunday 10 May 2009 18:04:35 Jim wrote:
>>>>>
>>>>>> I have a EeePC 1000 with two SSD drives and Fedora 10.
>>>>>> I want to make / partition larger
>>>>>> sda1 / 8gb
>>>>>> sdb1 /home 32gb
>>>>>>
>>>>>> I want to make /home 20gb
>>>>>> I want to make / 20gb
>>>>>>
>>>>>> I have made sdb1 /home 20gb with Gparted and I made with the
>>>>>> unallocated space a / ext3 primary partition.
>>>>>> how do I make that / partition to join with the / on sda1 ?
>>>>>>
>>>>>
>>>>> You will have to create a software RAID0 device that spans across
>>>>> both drives and includes all of the space you want used for /,
>>>>> then create a new partition for / within that RAID device.
>>>>>
>>>>>
>>>> What Raid Type would I use ?
>>>>
>>>
>>> You have 2 choices:
>>>
>>> 1) Create a RAID-0 partition which spans both drives. This results
>>> in a single partition. The drives need to be the same size in order
>>> for the striping to work. These drives are not the same size. You
>>> could stripe the first 8GB for a 16 GB partition, but it would leave
>>> you with a 24 GB 2nd partition on sdb, 16/24 is not quite what you
>>> want.
>>>
>>> 2) Use LVM to merge the 2 physical partitions into a single logical
>>> volume which spans both drives. Since both logical partitions can
>>> be allocated out of the single logical volume, you can make them
>>> whatever size you need (ie, both of 20GB should be doable).
>>>
>> I can make both partitions the same .
>> sda1 8gb
>> sdb2 8gb
>> Total 16gb for /
>>
>> And put the remainder in sdb1 /home.
>>
>> I guess I will settle for a Raid 0
>>
>> But how would a Raid 5 do ?
>
> You don't have enough disks for a real RAID-5. You need a minumum of
> 3 "disks". RAID-5 is designed so that you can be doing a write of
> data and a write of the "parity" data for each write. Reads can be
> done quicker since the more "disks" in your stripe, the better the
> possibility that 2 concurrent reads will use different disks to access
> the required data, possibly doing it faster (in parallel instead of
> serially) and with the possibility of still being able to access your
> data even if one of your disk drives fails (RAID-6 provides for a
> possible double failure by adding a 2nd parity disk in the array).
>
> Note: RAID-0 has no parity data, so no redundancy in case of hardware
> failure. But the striping could lead to quicker read or write times
> since you would have 2 disks to spread the operations over instead of
> having only one and having to wait for a previous operation to finish
> before doing a 2nd one.
>
> Your choices with only 2 physical spindles is either RAID-0 (striping)
> or RAID-1 (mirroring).
>
Thanks Kevin for your help on this.
Can I change a ext3 partition (sda1) with data on it to raid 0 or do I
have to do a fresh install ?
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