[Asterisk-Users] High capacity voicemail

[izo]

Hi,
Does anybody has experience with high capacity PSTN voicemail and
asterisk, running more then 5k mailboxes for PSTN users ?
How many mailboxes can I serve with 4xE1 card if we assume that we
have enough harddrive
capacity. What would be server requirements. Would the CPU load be the
same when storing
voicemails in gsm format as compresing to gsm for ip calls ? 
Any hints would be greatly appreciated

regards
m.